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GeoDIL Images

University of North Dakota

The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily intended as a teaching and learning resource for K-16 educators and students. This project was initiated at the University of North Dakota (UND) in fall 2000. Dexter Perkins and Joseph Hartman, of UND's Department of Geology and Geological Engineering, are the Library Directors.

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GeoDIL Images
by Darla Sondrol
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Turquoise Description: Turquoise, CuAl 6 (PO 4 ) 4 (OH) 8 *5(H 2 O) (hydrated copper aluminum phosphate), is a valuable mineral and is possibly the most valuable, non-transparent mineral in the jewelry trade. Its history also includes beautiful ornamental creations by Native Americans and Persians. Turquoise is often imitated by “fakes”, such as the mineral chrysocolla, and poorer turquoise specimens are often dyed or color stabilized with coatings of various resins. Location: USA ▹ New...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Quartz, amethyst Description: Amethyst, a variety of quartz (SiO 2 ) has been found in siliceous volcanics, occurring as macroscopic crystals and drusy coverings inside of agate lined amygdaloidal cavities or vugs, often forming geodes. Amethyst also occurs in quartz veins. The purple color of amethyst is due to small amounts (approximately 40 parts per million) of iron (Fe 4 + ) impurities at specific sites in the crystal structure of quartz. Location: Brazil. Near Minas Gerais. Collection:...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Aquamarine (beryl) Description: Aquamarine is the blue, blue-green or aqua variety of the mineral beryl (Be 3 A l2 Si 6 O 18 ). Aquamarine is colored by trace amounts of iron in the crystal structure. Some gem aquamarines have been heat treated to produce the popular blue-green colors from less desirable yellow or pale stones. This gem is an emerald cut aquamarine. This gemstone is courtesy of The Jewel Box , Grand Forks, ND. Collection: The Jewel Box Collection of Gemstones. Tech details: 64...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Ruby (corundum) from Mysore, India Description: Ruby is the red gemmy variety of corundum, Al 2 O 3 , one of the hardest minerals known. Gem corundum of any other color is called sapphire (although we generally think of sapphire as being blue). The red color in ruby is caused by trace amounts of chromium. The best shade of red for ruby is often given the name “pigeon blood red,” but ruby can be any shade of red to almost pink. This crystal is about 7 cm across. Location: USA ▹ India. Near...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Gypsum (selenite) Description: Clear gypsum is called selenite. These selenite crystals are about 7 cm in longest dimension. Gypsum has composition CaSO 4 •2H 2 O, and is one of the most common evaporite minerals. Location: Chile Collection: University of North Dakota Mineralogy Collection. Tech details: 521 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Rhodolite garnet Description: Rhodolite is a name sometimes used for red garnets with compositions between almandine (Fe 3 Al 2 Si 3 O 12 ) and pyrope (Mg 3 Al 2 Si 3 O 12 ). The name is derived from the Greek words rhodon and lithos, meaning rose-stone. This gem is an oval cut and is 3.15 carats. Collection: The Jewel Box Collection of Gemstones. Tech details: 104 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image Library (GeoDIL)...
Topics: geology, mineralogy
GeoDIL Images
by Shannon Heinle
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Heliotrope Description: Heliotrope is also known as bloodstone. Bloodstone is a green jasper dotted with bright red “blood” spots of iron oxide. It was treasured in ancient times and long served as the birthstone for March. This attractive chalcedony quartz is known as heliotrope because in ancient times polished stones were described as reflecting the sun. Many myths and powers are associated with bloodstone. Location: India Collection: University of North Dakota Mineralogy Collection...
Topics: geology, mineralogy
GeoDIL Images
by Joseph Hartman
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UND/NDSU students, GeoDIL librarians and administrators in action Description: UND/NDSU students, GeoDIL librarians and administrators in action. Collecting data for GeoDIL can be a demanding job. Location: USA ▹ Hawaii Tech details: 75 KB. Vista. Cannon EOS Rebel 55mm. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily intended as a teaching and learning resource for K-16 educators and students. This project was initiated at the University of...
Topics: geology, mineralogy
GeoDIL Images
by Nessa Eull
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Sapphire Description: To most mineralogists, sapphire refers to all varieties of corundum, Al 2 O 3 (aluminum oxide), that are partly to fully transparent and not red. In the gem trade, some people use sapphire to refer only to blue varieties. Location: India. Near Kashmir. Collection: University of North Dakota Mineralogy Collection #451. Tech details: 261 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image Library (GeoDIL) is a...
Topics: geology, mineralogy
GeoDIL Images
by Shannon Heinle
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Agate Description: Agate is a cryptocrystalline (crystals too small to be seen even by a microscope) variety of quartz. These varieties are divided more by character than by color. These different variatites are often used as semi-precious gemstones and for decorative purposes. Location: USA ▹ Montana Collection: University of North Dakota Mineralogy Collection #1630. Tech details: 478 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital...
Topics: geology, mineralogy
GeoDIL Images
by Nessa Eull
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Krohnkite Description: Krohnkite is a secondary copper mineral that is found in the oxidized zones of copper ore deposits. It has composition Na 2 Cu(SO 4 ) 2 ·2(H 2 O). The source of this specimen, 8 cm across, is unkown. Collection: University of North Dakota Mineralogy Collection. Tech details: 456 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily intended as a...
Topics: geology, mineralogy
GeoDIL Images
by Neil Kadrmas
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Dioptase, CuSiO 2 (OH) 2 Description: Dioptase is a relatively rare mineral, but is well known because many specimens are exceptionally beautiful. It is one of the few minerals that can be as vivid green as emerald. In some literature dioptase is refered to as “emerald copper.” Dioptase has composition CuSiO 2 (OH) 2 and forms in alteration zones of copper deposits. This sample comes from a famous locality at Altyn-Tube, in the Kirghese Steppes, Kazakhstan. Location: Kazakhstan. Near...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Fluorite Description: Fluorite, CaF 2 , commonly occurs as transparent crystals in a great variety of colors. Fluorite is not commonly fashioned into gems, since it is not durable enough to maintain a polish with normal jewelry use. This fluorite sample is courtesy of The Jewel Box , Grand Forks, ND. Collection: The Jewel Box Collection of Gemstones. Tech details: 102 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image Library...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Fancy Yellow Diamond Description: Diamond, elemental carbon (C), is the hardest substance found in nature, diamond is four times harder than the next hardest natural mineral, corundum (sapphire and ruby). Diamond comes from the Greek word “adamas,” meaning “I tame.” The beautiful hues of colored diamonds are caused by the presence and distribution of small amounts of nitrogen (yellow) or boron (blue) within the diamond. This sample is a cushion cut diamond, with the color/clarity rating...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Beryl, var. aquamarine Description: Beryl is a silicate with the chemical formula Be 3 Al 2 (SiO 3 ) 6 . Beryl is not a well known mineral and it comes in many color varieties. The green beryl, emerald and the blue beryl, aquamarine, are the most popular among gem collectors. Some varieties are fluorescent or insoluble in acids. Beryl is a very important economic mineral and the major source of beryllium. Location: Brazil. Near Minas Gerais. Collection: Ward’s Classroom Collection of Gem...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Intergrowth of quartz, sphalerite and pyrite from a hydrothermal deposit Description: This sample, 4 cm across, contains conspicuous prismatic quartz crystals, dark (nearly black) sphalerite, and golden pyrite. The specimen comes from a hydrothermal deposit in Huaron, Peru. Location: Peru. Near Huaron. Collection: University of North Dakota Mineralogy Collection. Tech details: 610 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Fluorite from Roxbury, Connecticut Description: This cleavage fragment of fluorite, CaF 2 , is about 6.5 cm across. Fluorite typically forms cubic crystals. Many sharp looking fluorite specimens are octahedral, but they are mostly cleavage fragments rather than whole crystals. Location: USA ▹ Connecticut. Near Roxbury. Collection: University of North Dakota Mineralogy Collection. Tech details: 605 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The...
Topics: geology, mineralogy
GeoDIL Images
by Dexter Perkins
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Limestone sea arch, south coast, Portugal Description: This photo shows a small sea arch, cut through limestone, near the southernmost point of Portugal. Location: Portugal Tech details: 462 KB. Outcrop. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily intended as a teaching and learning resource for K-16 educators and students. This project was initiated at the University of North Dakota (UND) in fall 2000. Dexter Perkins and Joseph Hartman, of...
Topics: geology, mineralogy
GeoDIL Images
by Nessa Eull
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Realgar and orpiment from Felsobanya, Hungary Description: Realgar, AsS (arsenic sulfide), is one of only a few sulfides that are non-metallic, opaque or blandly colored. Realgar occurs in hydrothermal veins with valuable metal sulfide ores and its bright red color is distinctive. Orpiment, As 2 S 3 (arsenic sulfide), is a rare mineral that usually forms with realgar. In fact the two minerals are almost always together. The yellow color is special to orpiment and can be confused only with a few...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Dolomite crystals on dolomitic mudstone Description: Here we see nicely formed rhombohedral crystals of dolomite, CaMg(CO 3 ) 2 (calcium magnesium carbonate). They crystallized on top of a slab of dolomitic mudstone. Dolomite crystals often have a beautiful pinkish color, pearly luster and unusual crystal habit that includes curved crystal faces. This sample is 14 cm across. Collection: University of North Dakota Mineralogy Collection #629. Tech details: 789 KB. Hand specimen. Fujifilm FinePix...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Diamond Description: Diamond, elemental carbon (C), is the hardest substance found in nature, but few people realize that diamond is four times harder than the next hardest natural mineral, corundum (sapphire and ruby). Diamond's single flaw (perfect cleavage) is far outdistanced by the sum of its positive qualities. It has a broad color range, high refraction, high dispersion or fire, very low reactivity to chemicals, rarity, and extreme hardness and durability. This sample is a oval cut...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Rhodochrosite and quartz Description: The pink and orange mineral is rhodochrosite, MnCO 3 . Most of the rest of the material white to gray is quartz. This sample is 6 cm across. Collection: University of North Dakota Mineralogy Collection #1927. Tech details: 871 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily intended as a teaching and learning resource for K-16...
Topics: geology, mineralogy
GeoDIL Images
by Dexter Perkins
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Comparison of granite (left) and arkose (right) Description: These samples of granite (on left) and arkose (on right) both contain the same minerals: predominately quartz and K-feldspar. Granite is an igneous rock, so the crystals interlock in a mosaic-like pattern. Arkose is a detrital sedimentary rock, so the crystals are piled together like grains of sand. The red color of both is due to iron oxidation. These samples are part of the Petrology teaching collection of the Department of Geology...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Natrochalcite Description: Natrochalite is an emerald green copper mineral from Chuquicamata, Chile. It is a secondary mineral, often forming in veins or crusts associated with copper ores. It has formula NaCu 2 (SO 4 ) 2 (OH,H 2 O) 2 . This specimen is 7.5 cm in longest direction. Location: Chile. Near Chuquicamata. Collection: University of North Dakota Mineralogy Collection #830. Tech details: 743 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The...
Topics: geology, mineralogy
GeoDIL Images
by Douglas Perkins
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Three sets of verb flashcards for EFL students.  Each set has twenty cards with a picture on the front and the verb written and conjugated on the back.  All standalone images are in the Public Domain.
Topics: English, EFL, ESL, flashcards
GeoDIL Images
by Joseph Hartman
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UND Hawaii Spring Break 2002 Description: You will find this no where else! Photos of martians Beth Eslinger and Darla Sondrol. The martians are standing on a recent aa flow in Hawaii. Location: USA ▹ Hawaii. Near Kona. Recent aa flows on the way to Kona. Collection: Joseph Hartman C9252. Tech details: 270 KB. Kodachrome, TIFF. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily intended as a teaching and learning resource for K-16 educators and...
Topics: geology, mineralogy
GeoDIL Images
by Neil Kadrmas
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Amazonite (microcline) Description: Amazonite is a term used to describe green to blue microcline that is sometimes used as a gemstone. More typically, microcline (a K-feldspar) is white to tan in color. In this photo, the “pseudo-hexagonal” nature of the feldspar crystals can be seen. This specimen is 7 cm across. It comes from a well-known collecting site at the Rocket Mining Claim, near Pikes Peak, Colorado. Location: USA ▹ Colorado. Near Colorado Springs. Rocket Mining Claim....
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Quartz with dolomite Description: This sample contains white quartz, SiO 2 (silicon dioxide), and brown dolomite, CaMg(CO 3 ) 2 (calcium magnesium carbonate). Both are common minerals. Quartz is often white (or clear), but this hue of brown is a bit uncommon for dolomite. The quartz crystals in this sample have quartz's typical hexagonal prismatic shape. Dolomite typically forms rhombohedrons but some crystals (such as the ones in this specimen) curve into elongate saddle-shaped crystals. This...
Topics: geology, mineralogy
GeoDIL Images
by Nessa Eull
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Clay ironstone nodule, from near Mazon Creek, Illinois, USA Description: This is a nodule (concretion) from Francis Creek Shale of the Carbondale Formation (Pennsylvanian) near Mazon Creek, Illinois. These concretions, which developed through action of groundwater after the shale was deposited, are made of ironstone, and are mineralogically siderite ( FeCO 3 = iron carbonate) with minor clay. These nodules are famous because many of them, when broken, reveal spectacular plant and animal...
Topics: geology, mineralogy
GeoDIL Images
by Shannon Heinle
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Graphic granite Description: This rock typically consists of nearly parallel rodlike masses of quartz (SiO 2 ) surrounded by feldspar (XAl (1-2) Si (3-2) O 8 ). It is used as gemstones for pieces such as pendants and for fashioning ornaments, particularly relatively large ones such as bookends. It can be found anywhere where granite is. Location: Canada ▹ Ontario Collection: University of North Dakota Mineralogy Collection #1696. Tech details: 478 KB. Hand specimen. Fujifilm FinePix S1Pro...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Rose quartz Description: Rose quartz, SiO 2 (silicon dioxide), is opaque to translucent macrocrystalline quartz of pink to rose-red color. It normally occurs in the cores of large pegmatites as solid masses of rose colored quartz whose individual crystals have poorly formed boundaries. The color of rose quartz is still not completely understood. It has been said to be due to a number of different minor impurities present including titanium, manganese and even colloidal gold. Location:...
Topics: geology, mineralogy
GeoDIL Images
by Mike Davis
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Lamprophyre, Spanish Peaks, Colorado Description: This lamprophyre is a dark gray uniformly fine-grained rock. Lamprophyres are dark colored igneous rocks, often having the general appearance of basalt. Lamprophyres, however, are closer to andesite in composition and typically contain biotite (phlogopite). Although not identifiabled in this photograph, the fine mineral grains consist of olivine, magnetite, augite, plagioclase and biotite. This specimen is 8 cm across. Lamprophyres may also...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Hematite Description: Hematite (Fe 2 O 3 ), an oxide of iron, is a very common mineral and the main ore of iron. It occurs in hydrothermal veins and in sedimentary deposits, and is also found as a minor constituent of some igneous rocks. Collection: University of North Dakota Mineralogy Collection #82. Tech details: 662 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Gypsum (selenite), CaSO 4 •2H 2 O Description: Gypsum has many different appearances. Most commonly it is massive and opaque. Clear samples, like this one are called selenite. This specimen is 8 cm across. Collection: University of North Dakota Mineralogy Collection #797. Tech details: 1016 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily intended as a teaching...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Sphaerocobaltite from Sudbury, Ontario, Canada Description: The pink mineral is sphaerocobaltite, CoCO 3 (cobalt carbonate), also sometimes called (incorrectly) cobaltocalcite and cobaltian-calcite. (The latter two names are more appropriate for referring to calcite that has an appreciable amount of cobalt in its structure as an impurity.) The sometimes deep rose-red to pink color of this mineral can be very attractive and unique. Sometimes sphaerocobaltite can be confused with other pinkinsh...
Topics: geology, mineralogy
GeoDIL Images
by Joseph Hartman
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A “final” resting place for Hell Creek mollusks Description: A “final” resting place for Hell Creek Formation mollusks, University of North Dakota, Grand Forks, North Dakota. Chronostratigraphy: Upper Cretaceous. Lithostratigraphy: Hell Creek Formation. Geologic province: Williston Basin. Location: USA ▹ North Dakota ▹ Grand Forks. Near Grand Forks. Hartman paleocabinet. Collection: Joseph Hartman C8804. Tech details: 214 KB. Ektachrome, TIFF format. The Geoscience Digital Image...
Topics: geology, mineralogy
GeoDIL Images
by Dexter Perkins
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Puy de Pariou and Puy de Dome, Auvergne, France Description: The Massif Central in the center of France (Auvergne region), contains a range of volcanoes made up of the Monts Dome (1465 meters at the Puy de Dome) and the Monts Dore (1886 meters at the Puy de Sancy). Eruptions included both Peleean (involving the formation and collapse of lava domes) and Strombolian (lava fountains and ejection of cinders, lapilli, blocks and bombs). The last eruptions were about 4,000 years ago. The region...
Topics: geology, mineralogy
GeoDIL Images
by Shannon Heinle
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Serpentine Description: Serpentine is a magnesium iron silicate hydroxide. Serpentine is a major rock forming mineral and is found as a constituent in many metamorphic and weather igneous rocks. It often colors many of these rocks to a green color and most rocks that have a green color probably have serpentine in some amount. Serpentine is a general name applied to several members of a polymorphic group. It has been used as a substitute for jade and is sometimes difficult to distinguish from...
Topics: geology, mineralogy
GeoDIL Images
by Nessa Eull
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Cinnabar from New Almaden, California Description: Cinnabar, HgS (mercury sulfide), typically has a vermillion to red color. It has been used as a pigment, but more importantly as an ore of the metal mercury. It is mined in many places, including most famously Spain and Italy. This sample comes from a mine near New Almaden, California, USA. It is 8 cm across. Location: USA ▹ California. Near New Almaden. Collection: University of North Dakota Mineralogy Collection #205. Tech details: 619 KB....
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Rhodolite (pyrope-almandine garnet) Description: Rhodolite is the rasberry pink to wine colored variety of pyrope-almandine garnet, (Mg,Fe) 3 Al 2 Si 3 O 12 . This gem is a fantasy cut rhodolite and is 4.40 carats. Collection: The Jewel Box Collection of Gemstones. Tech details: 106 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily intended as a teaching and learning...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Hematite ore from the Upper Huronian Biwabik Formation, Minnesota Description: Hematite, Fe 2 O 3 (iron oxide), is an important ore of iron and it's red color makes it useful as a pigment. Hematite gets its name from a Greek word meaning blood-like because of the color of its powder. Ancient superstition held that large deposits of hematite formed from battles that were fought and the subsequent blood that flowed into the ground. Visible crystals of hematite are rare; most samples are very fine...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Tourmaline from pegmatite, Brazil Description: Tourmaline comes in many different colors. The pink variety is called rubellite. More typically, tourmaline is black (schorl) but even black varieties can shine or sparkle. High quality tourmalines are prized as gems. Tourmaline is the most common mineral that contains boron. This crystal is 6 cm long. Location: Brazil. Near Gouvernador Valaderas. Collection: University of North Dakota Mineralogy Collection. Tech details: 492 KB. Hand specimen....
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Green tourmaline Description: These samples of tourmaline are not of sufficient quality to be considered gems, but many samples from California are. Most people consider tourmaline to be a single mineral. But in fact it is a group of closely related mineral varieties with different colors. Green tourmaline is called verdelite; often the green in more pronounced than in this photograph. These crystals are 6 cm long. Location: USA ▹ California ▹ San Diego County Collection: University of...
Topics: geology, mineralogy
GeoDIL Images
by Shannon Heinle
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Topaz from Topaz Mountain, Utah Description: Topaz is a common gemstone, sometimes confused with citrine. Chemically, it is an aluminum silicate fluoride hydroxide, Al 2 SiO 4 (F,OH) 3 . The crystals in this photo come from Topaz Mountain, in the Thomas Range, Utah. They are in a light gray to white rhyolite, some of which can be seen in the photo (attached to the largest crystal). Topaz Valley, the main topaz collecting area, was set aside by the Bureau of Land Management as a rockhound area....
Topics: geology, mineralogy
GeoDIL Images
by Dexter Perkins
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Navajo Sandstone, Wingate Sandstone, Chinle Formation, and Moenkopi Formation exposed in a cliff, Capitol Reef National Park Description: This photo shows the Moenkopi Formation (red castellated outcrop near bottom of cliff), overlain by the Chinle Formation (grennish to red slope), overlain by the steep Wingate Sandstone cliff. In the far distance, just barely visible is the whitish Navajo Sandstone. All are of Triassic age, although in some parts of Utah the Navajo Sandstone is considered...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Opal Description: Opal, SiO 2 -nH 2 O (hydrated silicon dioxide), is considered a mineraloid because its structure is not truly crystalline. The chemistry of opal is primarily SiO 2 and varying amounts of water from 5%-10% and greater. This water can help geologists determine the temperature of the host rock at the time the opal formed. The gem in this photo is courtesy of: The Jewel Box , Grand Forks, ND. Collection: The Jewel Box Collection of Gemstones. Tech details: 38 KB. Hand specimen....
Topics: geology, mineralogy
GeoDIL Images
by Nessa Eull
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Apatite crystals Description: Apatite, Ca 5 (PO 4 ) 3 (OH,F,Cl) is the most common phosphate mineral. It is present in many rocks of different sorts but is generally too fine grained and disseminated to be seen easily. It sometimes forms in massive beds (phosphorites) which are mined to manufacture fertilizers and other chemicals. Coarse gemmy crystals, such as the 1 cm long crystals shown here, form in some metamorphic rocks. Well-formed apatite crystals are hexagonal prisms, but the hexagonal...
Topics: geology, mineralogy
GeoDIL Images
by Shannon Heinle
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Carnelian Description: Carnelian is a yellow to orange agate. Agate is a cryptocrystalline (crystals too small to be seen even by a microscope) variety of quartz. These varieties are divided more by character than by color. These different variatites are often used as semi-precious gemstones and for decorative purposes. Location: USA ▹ Colorado Collection: University of North Dakota Mineralogy Collection #1628. Tech details: 233 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm...
Topics: geology, mineralogy
GeoDIL Images
by Nessa Eull
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Calcite with quartz and ankerite, Galena, New Mexico Description: This is a geode containing calcite, CaCO 3 , with quartz, SiO 2 , and ankerite, CaFe(CO 3 ) 2 . The ankerite is brown, the calcite is the large white crystals, and the quartz is all in small crystals on the interior wall of the geode. This sample comes from Galena, New Mexico, and is about 6 cm across. Location: USA ▹ New Mexico. Near Galena. Collection: University of North Dakota Mineralogy Collection #642. Tech details: 677...
Topics: geology, mineralogy
GeoDIL Images
by Shannon Heinle
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Microcline Description: Microcline belongs to the Feldspar Group. Microcline is a common, but not a well known mineral. Some forms of microcline, such as amazonite and perthite, have been used as semi-precious stones. Microcline is a polymorph of other minerals that share the same chemistry, but have different crystal structures. Its mineral formula is KAlSi 3 O 8 . Microcline comes from the Greek mikron meaning “little” and klinein meaning “to stoop”. Location: USA ▹ Colorado. Near...
Topics: geology, mineralogy
GeoDIL Images
by Joseph Hartman
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Nashville Description: Nashville, TN. Location: USA ▹ Tennessee. Near Nashville. Collection: Joseph Hartman C8792. Tech details: 403 KB. Outcrop. Ektachrome. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily intended as a teaching and learning resource for K-16 educators and students. This project was initiated at the University of North Dakota (UND) in fall 2000. Dexter Perkins and Joseph Hartman, of UND's Department of Geology and Geological...
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GeoDIL Images
by Dexter Perkins
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Tabular barite with calcite and pyrite, from Joplin, Missouri, USA Description: Large tan barite (BaSO 4 ) tabs, some appearing pseudo-hexagonal, are embedded in finer white calcite, CaCO 3 . Pyrite crystals, FeS 2 , generally about 1 mm across are scattered in the sample. No provenance data is available except that it comes from Joplin, Missouri, USA. This photo is about 5 cm across. Location: USA ▹ Missouri. Near Joplin. Collection: University of North Dakota Mineralogy Collection. Tech...
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GeoDIL Images
by Joseph Hartman
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Supai Group sandstones, Grand Canyon National Park, Arizona Description: View of cross bedding and exfoliation of Supai Group in North Canyon off Marble Canyon, Grand Canyon National Park. Chronostratigraphy: Lower Pennsylvanian to Lower Permian. Lithostratigraphy: Supai Group. Geologic province: Colorado Plateau. Location: USA ▹ Arizona ▹ Coconino. Near Grand Canyon. Grand Canyon National Park. Collection: Joseph Hartman P06105. Tech details: 751 KB. Outcrop. Kodachrome, TIFF format. The...
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GeoDIL Images
by Dexter Perkins
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Aurichalcite from Salt Lake County, Utah Description: Aurichalcite, (Zn,Cu) 5 (CO 3 ) 2 (OH) 6 is one of the many blue or green copper-bearing minerals. It is most typically found in the oxidized portions of copper ore deposits, where it may be associated with other colorful minerals such as azurite, smithsonite or (in this case) limonite. This specimenis 8 cm across. Location: USA ▹ Utah ▹ Salt Lake. Near Salt Lake. Collection: University of North Dakota Mineralogy Collection #742. Tech...
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GeoDIL Images
by Dexter Perkins
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Hot basalt in Hawaii Volcanoes National Park Description: Hawaii Volcanoes National Park has had nearly continuous basaltic eruptions for many years. During the past decade (1995-2005), intrepid hikers have walked out from the Chain of Craters Road to see the hot lava while it is still glowing, and where it (sometimes) enters the ocean. The flow shown here comes from the Puu Oo vent of Kilauea Volcano. The field ov view is about 6 feet across. Location: USA ▹ Hawaii. Near Hilo. Hawaii...
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GeoDIL Images
by Darla Sondrol
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Diamond Description: Diamond, elemental carbon (C), is the hardest substance found in nature, but few people realize that diamond is four times harder than the next hardest natural mineral, corundum (sapphire and ruby). Diamond's single flaw (perfect cleavage) is far outdistanced by the sum of its positive qualities. It has a broad color range, high refraction, high dispersion or fire, very low reactivity to chemicals, rarity, and extreme hardness and durability. This sample is ideal cut, with...
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GeoDIL Images
by Shannon Heinle
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Sylvite from Esterhazy, Saskatchewan Description: Sylvite, KCl, is a mineral very similar to halite, NaCl. It is sometimes used as a substitute for regular commercial salt. This sample is 6 cm across. Location: Canada ▹ Saskatchewan. Near Esterhazy. Collection: University of North Dakota Mineralogy Collection #328. Tech details: 411 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science...
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GeoDIL Images
by Shannon Heinle
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Zircon Description: Zircon, ZrSiO 4 , is a tetragonal mineral (ideal crystals have a square cross section when viewed in one direction) but it does not show here. Zircon is found in magmatic, metamorphic, pegmatitic, and alluvial rock environments. Zircon is the principle ore mineral for zirconium, and some zircon crystals are beautiful enough to be gems. Zircon is NOT the same material as the artificial gem material Cubic Zirconia. However, zircon has been used as a diamond simulant because it...
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GeoDIL Images
by Darla Sondrol
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Hematite Description: Hematite, Fe 2 O 3 (iron oxide), may have any of a number of different colors. This sample is metallic steel gray to iron black. Samples that are especially sparkly and metallic are called specular hematite . Many samples of hematite are orange, red or brown, and a hint of those colors can be seen here. Hematite has historically been an important ore of iron. This specimen is 9 cm across. Location: USA ▹ Michigan Collection: University of North Dakota Mineralogy...
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GeoDIL Images
by Joseph Hartman
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Steinacker Reservoir, Carmel Silicified Fossils Description: Steinacker Reservoir, Carmel Silicified Fossils. Location: USA ▹ Utah Collection: Joseph Hartman P02719 vol. 3-121. Tech details: 362 KB. Outcrop. Etkachrome; TIFF Format. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily intended as a teaching and learning resource for K-16 educators and students. This project was initiated at the University of North Dakota (UND) in fall 2000. Dexter...
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GeoDIL Images
by Darla Sondrol
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Quartz, jasperized wood (tumbled) Description: Jasperized wood (xyloid jasper) is petrified wood. It is wood that has fossilized - all the original chemicals have been replaced with minerals, making a stone-like replica of the original wood. Location: USA ▹ Arizona. Near Holbrook. Collection: Wards Classroom Collection of Gem Minerals #20. Tech details: 146 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image Library (GeoDIL) is a...
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GeoDIL Images
by Darla Sondrol
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Rhodochrosite with pyrite and wad in dolomite Description: The pinkish rhombs on top, and the fine grained pink material below are both rhodochrosite, MnCO 3 (manganese carbonate). Rhodochrosite is closely related to calcite (calcium carbonate). The white mineral is dolomite (calcium magnesium carbonate), and the darker areas contain mixtures of manganese oxides (sometimes termed “wad”). Minor, hard to see fine-grained pyrite (iron sulfide) is scattered in this sample. This specimen is 9 cm...
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GeoDIL Images
by Shannon Heinle
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Albite Description: Albite is a common felspar and is the “pivot” mineral of two different feldspar series. Albite is the last of the feldspars to crystallize from molten rock. All plagioclase feldspars show a type of twinning that is named after albite. Albite's chemical formula is NaAlSi 3 O 8 . The name comes from the Latin, albus, in allusion to the common color. Location: USA ▹ Virginia. Near Ameila Courthouse. Collection: University of North Dakota Mineralogy Collection #1691. Tech...
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GeoDIL Images
by Nessa Eull
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Cinnabar with metacinnabar Description: Cinnabar (HgS) is a mercury sulfide that typically has a vermillion to pink or scarlet color. Metacinnabar (a different mineral) has the same composition but a black or gray color, and sometimes a metallic luster. Both are important ore minerals of mercury. This specimen, a fine grained mix of both minerals, is about 8 cm in longest dimension. Collection: University of North Dakota Mineralogy Collection #187. Tech details: 423 KB. Hand specimen. Fujifilm...
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GeoDIL Images
by Nessa Eull
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Rosasite and calcite Description: Rosasite, (Cu,Zn) 2 CO 3 (OH) 2 , forms in the oxidation zones of zinc-copper deposits. It typically is found as attractive bluish-green crusts and forms botryoidal masses or nodules. Crystals also may be fibrous and in tufted aggregates. Rosasite is associated with red limonite and other such colorful minerals as aurichalcite, smithsonite and hemimorphite. Here it is also seen with white and gray crystals of calcite. This sample is 9 cm across. Location:...
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GeoDIL Images
by Dexter Perkins
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Death Valley National Park from Daunte's View Description: Death Valley National Park from Daunte's View. Location: USA ▹ California. Near Death Valley. Collection: E451202991V. Tech details: 440 KB. Vista. Canon Eos Rebel, 55mm lens, Kodak Ektachrome Elite. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily intended as a teaching and learning resource for K-16 educators and students. This project was initiated at the University of North Dakota...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Halite and sylvite Description: Halite (NaCl) and sylvite (KCl) are often found together. Although similar in chemistry and crystal structure, their mutual solubility is limited, so compositions between the two are very rare. In this sample the halite is stained red, but halite is usually clear white. This specimen is about 18 cm. Collection: University of North Dakota Mineralogy Collection. Tech details: 701 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens....
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GeoDIL Images
by Nessa Eull
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Manganiferous nodule from Biwabik Formation Description: Manganiferous nodule from Biwabik Formation. Location: USA ▹ Minnesota. Near Hibbing. Albany Pit. Collection: University of North Dakota Mineralogy Collection #3436. Tech details: 568 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily intended as a teaching and learning resource for K-16 educators and...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Banded limonite-hematite and greenalite Rock Description: Banded hematie-limonite and greenlite rock from the upper Huronian, Biwabic Formation. Limonite is not a true mineral, but a mixture of similar hydrated iron oxide minerals. Hematite, Fe 2 O 3 (iron oxide), is an important iron ore. Location: USA ▹ Minnesota. Near Hibbing. Albany Pit. Collection: University of North Dakota Mineralogy Collection #3641. Tech details: 1.03 MB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF...
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GeoDIL Images
by Joseph Hartman
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Modern Corals Description: Modern Corals. Location: USA Collection: Joseph Hartman P02268. Tech details: 206 KB. Kodachrome, TIFF format. The Geoscience Digital Image Library (GeoDIL) is a collection of Earth science images primarily intended as a teaching and learning resource for K-16 educators and students. This project was initiated at the University of North Dakota (UND) in fall 2000. Dexter Perkins and Joseph Hartman, of UND's Department of Geology and Geological Engineering, are the...
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Ruby and zoisite Description: Ruby (Al 2 O 3 ) is created when zoisite (Ca 2 Al 3 (SiO 4 ) 3 (OH)) is heat treated. The green color mineral is zoisite and the red is the ruby. This rock is about 9.5 cm on its longest axis. This rock is courtesy of: The Jewel Box , Grand Forks, ND. Collection: The Jewel Box Collection of Rocks. Tech details: 463 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. The Geoscience Digital Image Library (GeoDIL) is a collection of...
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GeoDIL Images
by Joseph Hartman
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Upper Cretaceous Lameta Formation and Deccan Traps, Lameta Ghat, near Jabalpur, India Description: View across Lameta Formation toward Deccan Trap basalts on other side of Narmada River. Geologic section located on eastern edge of Deccan Plateau, at Lameta Ghat, near Jabalpur, India. Chronostratigraphy: Upper Cretaceous. Lithostratigraphy: Lameta Formation, Deccan Traps. Geologic province: Deccan Plateau. Location: India ▹ Madhya Pradesh. Near Jabalpur. Collection: Joseph Hartman C04073. Tech...
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GeoDIL Images
by Joseph Hartman
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Saddle Canyon Hike in Grand Canyon with a View of Temple Butte Lens, Coconino County, Arizona Description: The Temple Butte Limestone consists medium bedded limestone of a purplish-gray to a pinkish-gray color. The lens vary in size, but often have a conglomeritic zone near the base. Chronostratigraphy: Devonian. Lithostratigraphy: Temple Butte Limestone. Geologic province: Colorado Plateau. Location: USA ▹ Arizona ▹ Coconino. Near Grand Canyon. Temple Butte. Collection: Joseph Hartman...
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GeoDIL Images
by Mike Davis
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Vishnu schist, Grand Canyon, Arizona Description: This sample of the Precambrian Vishnu Schist is quite fine grained. Mineral identification is difficult in hand specimen, but in thin section biotite, muscovite, quartz and plagioclase are easily seen. The Vishnu Schist is one of the oldest rock units in the Grand Canyon, and in North America. This schist averages about 1,700 to 2,000 million years old. This specimen is 9.5 cm across. Chronostratigraphy: Precambrian. Location: USA ▹ Arizona....
Topics: geology, mineralogy
GeoDIL Images
by Darla Sondrol
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Erythrite Description: Erythrite, Co 3 (AsO 4 ) 2 -8H 2 O (hydrated cobalt arsenate), is a wonderful mineral for people who like striking, unusual colors. Its characteristic bright red-purple color is very noticable and was used to spot veins of cobalt-bearing ore. Erythrite, or “cobalt bloom” as it is called by miners, is a weathering product of cobalt-containing minerals such as cobaltite. Most erythrite is found in the form of crusts, but specimens from Morocco have larger crystals. The...
Topics: geology, mineralogy