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Herkimer Diamond Mines
Some of the best places to find “Herkimer diamonds” today are located along New York State Routes 28 and 29 near Middleville, New York. (When visiting this area it is important to remember that all land in New York either belongs to the government or is private property. Collecting minerals from government lands is illegal…
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Physical Properties of “Herkimer Diamonds”
“Herkimer diamonds” share most of the physical properties of other forms of quartz. They are almost always transparent and range from colorless to smoky in color. “Herkimer diamonds” are, by definition, doubly terminated; however, they are known to occur in a wide range of crystal forms (see illustration). The crystals contain a wide range of inclusions.…
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Who Discovered “Herkimer Diamonds”?
The “Herkimer diamonds” of New York are not a recent discovery. The Mohawk people and early settlers knew about the crystals. They found them in stream sediments and plowed fields. They were amazed with the crystals and immediately held them in high esteem. People used the crystals as amulets, used them to make tools, and…
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Herkimer Diamond Geology and Geography
The host rock of “Herkimer diamonds” is the Cambrian-age, Little Falls Dolostone. The Little Falls Dolostone was deposited about 500 million years ago, and the “Herkimer diamonds” formed in cavities within the dolostone. These cavities are frequently lined with drusy quartz crystals and are often coated with a tarry hydrocarbon. Although Herkimer County, New York is…
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What are “Herkimer Diamonds”?
“Herkimer diamonds” is the name given to the doubly terminated quartz crystals found in Herkimer County, New York and surrounding areas. Examples of these crystals are shown in the photos on this page. Herkimer diamonds have the typical crystal habit of quartz; however, however, instead of having a termination on one end they are doubly terminated. This…
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Smithsonite Gemology
Smithsonite with excellent color and clarity is often cut into faceted gems and cabochons. It is rarely used in jewelry because it has a Mohs hardness of only 4 to 4.5 and would be quickly scratched and abraded even with careful wear. The accompanying photos show a faceted oval of translucent yellow smithsonite and a teardrop-shaped cabochon cut…
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Smithsonite vs. Hemimorphite
Smithsonite and hemimorphite are two very different minerals. Smithsonite is a carbonate mineral and a member of the trigonal crystal system, while hemimorphite is a silicate mineral and orthorhombic. They also have noticeable differences in specific gravity and cleavage. Even with these differences, the two minerals were confused with one another and identified by the name “calamine”…
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Geologic Occurrence
Smithsonite is a secondary mineral found in the rocks above and around many important zinc deposits. These smithsonite occurrences are often seen at the surface or at shallow depths. As a result, smithsonite was one of the earliest zinc minerals to be discovered and mined by pioneer metallurgists. Finding smithsonite at the surface has led to the…
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What is Smithsonite?
Smithsonite is a zinc carbonate mineral with a chemical composition of ZnCO3. Today it is a minor ore of zinc, but in the early days of metallurgy it was one of the most important ores. Typical smithsonite colors are brown, gray, white, green, and yellow. Translucent specimens in vibrant blue, green, pink, and yellow colors are favorites…
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A Gemologist’s View of Luster
Most geologists, including the author of this article, have not thought as deeply about luster as gemologists. If you open almost any mineralogy textbook to the pages that describe a mineral, the luster is usually given as one or two of the adjectives listed above. For example: submetallic to metallic. The author completed the coursework…