Category: Minerals


Diamond Mines in the United States Minerals

Diamond Mines in the United States

The world's leading consumer of diamonds has almost no production. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist United States diamonds: A photograph of several diamonds found at the Crater of Diamonds State Park, near Murfreesboro, Arkansas. These diamonds were probably nicely formed crystals when they were in the Earth's mantle.

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Corundum Minerals

Corundum

Corundum has historically been used as an abrasive, but it is most famous as the mineral of ruby and sapphire. Article by: Hobart M. King, Ph.D., RPG Corundum: Two corundum crystal segments from India showing the mineral's hexagonal crystal form and basal parting. These specimens are red in color and might be called "ruby corundum.

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Garnet Minerals

Garnet

Best known as a red gemstone. It occurs in many colors and has numerous industrial uses. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Gem garnets: Most people think that garnet is a red gemstone. However, garnet occurs in a wide variety of colors. Clockwise from the top left: red almandine (Madagascar), green tsavorite (Tanzania), yellow mali (Mali), orange spessartite (Mozambique), pink malaya (Tanzania), green merelani mint (Tanzania), red pyrope (Ivory Coast), green demantoid (Namibia), purple rhodolite (Mozambique), and orange hessonite (Sri Lanka).

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Chalcopyrite Minerals

Chalcopyrite

The world's most important ore of copper for at least five thousand years. Article by: Hobart M. King, Ph.D., RPG Auriferous Chalcopyrite: A specimen of chalcopyrite with pyrrhotite from the Rouyn District, Quebec, Canada. Some chalcopyrite contains enough gold or silver that it can be an ore of those metals without considering the copper content.

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Variscite Minerals

Variscite

A rare mineral sometimes used as a gem material. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Variscite nodules: Nodules of variscite with crandallite and wardite from Clay Canyon, Fairfield, Utah. Specimen sizes, clockwise from top left: 7.5 x 5.9 cm; 6.8 x 5.6 cm; 11.1 x 6.6 cm; 17.5 x 13.

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Bornite Minerals

Bornite

A copper iron sulfide mineral often called "peacock ore" because of its tarnish. Article by: Hobart M. King, Ph.D., RPG Bornite ore with light tarnish from the Copper Queen Mine, near Bisbee, Cochise County, Arizona. Specimen is approximately 7 x 5 x 4 centimeters. Specimen and photo by Arkenstone / www.

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Turquoise Minerals

Turquoise

A gem material that has been held in highest regard for thousands of years. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Turquoise Rough and Cabochons: A small collection of turquoise cabochons and pieces of uncut turquoise. The photographer and owner of the turquoise is Reno Chris of Nevada Outback Gems.

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Cordierite and the Gem Known as "Iolite" Minerals

Cordierite and the Gem Known as "Iolite"

Cordierite is the mineral known as "Iolite" when it is of gem quality. Article by: Hobart M. King, Ph.D., RPG Iolite: A blue-violet iolite faceted from material mined in Madagascar. This specimen is approximately 9.4 x 7.1 x 4.8 millimeters in size and weighs about 1.83 carats. A nice iolite like this one could easily serve as an alternative gem for sapphire or tanzanite at a much lower price.

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Silver Minerals

Silver

The soft, white, native metallic element with a diversity of uses. Article by: Hobart M. King, Ph.D., RPG Silver crystals: Crystals of native silver on calcite from the New Nevada Mine, Batopilas, Chihuahua, Mexico. Specimen is approximately 11 x 7 x 6 centimeters in size. Specimen and photo by Arkenstone / www.

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Dolomite Minerals

Dolomite

A common rock-forming mineral and the primary constituent of a sedimentary rock known as "dolostone" Article by: Hobart M. King, Ph.D., RPG Dolomite crystals: Dolomite crystals from Penfield, New York. This specimen is approximately 3 inches (6.7 centimeters) across. Dolomite: A Mineral and a Rock "Dolomite" is a word that is used by geologists in two different ways: 1) as the name of the mineral dolomite; and, 2) as the name of a rock known as dolomite, dolostone, or dolomite rock.

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Talc: The Softest Mineral Minerals

Talc: The Softest Mineral

What is Talc? How Does it Form? How is Talc Used? Article by: Hobart M. King, Ph.D., RPG Uses of talc: Talc is used in a wide variety of products that we see every day. It is an important ingredient in rubber, a filler and whitener in paint, a filler and brightening agent in high-quality papers, and a primary ingredient in many types of cosmetics.

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Green Diamonds Minerals

Green Diamonds

One of the rarest and most valuable diamond colors Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Green Diamond: This green diamond has all of the characteristics of a highly desirable colored diamond: A) it is a natural diamond; B) the green color was produced by nature; and, C) the color is a pure green with a rich saturation.

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Diamond Minerals

Diamond

The most popular gemstone. The hardest known substance. An amazing number of uses. Author: Hobart M. King, Ph.D., GIA Graduate Gemologist Diamond Crystal: A gem-quality diamond crystal in the rock in which it was formed. It is an octahedral crystal with triangular dissolution features on its surface and an estimated weight of about 1.

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Diopside Minerals

Diopside

A pyroxene mineral found in igneous and metamorphic rocks. A minor gemstone. Article by: Hobart M. King, Ph.D., RPG Chromium Diopside: A gemmy green specimen of chromium diopside from the the Outokumpu copper-zinc in Finland. This specimen measures 6.5 x 6.2 x 2.9 centimeters in size. Specimen and photo by Arkenstone / www.

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Fluorescent Minerals Minerals

Fluorescent Minerals

Learn about the minerals and rocks that "glow" under ultraviolet light Article by: Hobart M. King, Ph.D., RPG Fluorescent minerals: One of the most spectacular museum exhibits is a dark room filled with fluorescent rocks and minerals that are illuminated with ultraviolet light. They glow with an amazing array of vibrant colors - in sharp contrast to the color of the rocks under conditions of normal illumination.

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Chlorite Minerals

Chlorite

A group of common sheet silicate minerals Article by: Hobart M. King, Ph.D., RPG Chlorite: Chlorite from Quebec, Canada. This specimen is approximately 3 inches (7.6 centimeters) across. What is Chlorite? "Chlorite" is the name of a group of common sheet silicate minerals that form during the early stages of metamorphism.

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Biotite Minerals

Biotite

Biotite is group of common rock-forming minerals found in igneous and metamorphic rocks. Article by: Hobart M. King, Ph.D., RPG Biotite: Biotite from Bancroft, Ontario, Canada. Specimen is approximately 4 inches (10 centimeters) across. What is Biotite? Biotite is a name used for a large group of black mica minerals that are commonly found in igneous and metamorphic rocks.

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Ilmenite Minerals

Ilmenite

A black iron titanium oxide mineral. The primary ore of titanium, source of titanium dioxide. Article by: Hobart M. King, Ph.D., RPG Ilmenite: A specimen of massive ilmenite from Saint-Urbain, Quebec, Canada. Massive ilmenite can be formed as a vein-filling material or during magmatic segregation. This specimen is approximately 4 inches (10 centimeters) across.

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Augite Minerals

Augite

A common rock-forming mineral of dark-colored igneous rocks. Article by: Hobart M. King, Ph.D., RPG Augite: A specimen of the "jeffersonite" variety of augite. Approximately 11 x 6.3 x 4.3 centimeters in size. From the Franklin Mining District of Sussex County, New Jersey. Specimen and photo by Arkenstone / www.

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Vanadinite Minerals

Vanadinite

An important ore of vanadium and a minor source of lead. Article by: Hobart M. King, Ph.D., RPG Vanadinite: A cluster of orangy-brown vanadinite crystals on goethite collected from the Meknes-Tafilalet Region of Morocco. The largest vanadinite crystals are about 8 millimeters across, and the entire specimen is about 4.

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