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Edna B. Anthony

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Edna B. Anthony

Article
Benitoite Gems

One of the most beautiful blue gemstones is native to our own country. In 1906, a prospector found what he thought were sapphire crystals in the Diablo Mountain range of San Benito County, California. A year later, mineralogist, G. D. Louderback,…

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Cyclosilicate: Aquamarine

The region of pegmatite dikes in the state of Minas Gerais in Brazil has been the primary source of gem beryl and several other species of colored gemstones for many years. Rivers have cut places through the dikes and alluvial deposits, called…

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Cyclosilicate: Axinite

On an excursion in the Alps in 1797, mineralogist, R. J. Hauy discovered some highly vitreous, piezio-electric wedged-shaped crystals that resembled schorl, the dark variety of tourmaline. The incorrect designation, ‘vitreous schorl’,…

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Cyclosilicate: Dioptase

Dioptase incorporates the native metal, copper in the Si6O18 ring structure with water to form the only gem material that so closely approaches the finest color of emerald. The small and well-defined deep green rhombohedral crystals develop…

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Goshenite – Transparent, Colorless Beryl

Goshenite is the transparent, colorless, alkali-bearing pure beryl that was discovered in Goshen, Hampshire County, Massachusetts. The Lily Pond mine in a pegmatite near a small lake was the source of crystals accompanied by other pale…

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Introduction to Silicates

Silicates comprise about a quarter of the known minerals and almost 40% of the common ones. The basic unit of structure of all silicate crystals is the tetrahedron. There are four oxygen atoms, one located at each apex of a regular tetrahedron.…

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Kyanite Gemstone Properties

Andalusite, kyanite, and sillimanite all contain identical amounts of aluminum, silicon, and oxygen, combined with other trace elements. I find it intriguing to note the differences in how the chemical formulas for these three minerals…

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Let’s Talk Gemstones – Opal Part 1

Opal is a fascinating gemstone with an ancient history. Pliny the Elder gives an eloquent description of opal, comparing its many colors to that of the finest of ruby, emerald, sapphire, topaz, and amethyst. Romans prized opal so highly that…

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Let’s Talk Gemstones – Opal Part 2

Australia’s most famous opal mines lie on the periphery of this Great Artesian Basin. Mintabie, Coober Pedy, Andamooka, White Cliffs, and Lightning Ridge form an arc along its southern edge. Yowah, Quilpie, and Opalton project on a line north/northwest…

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Let’s talk Gemstones – Staurolite

Staurolite! Why would one of the most ordinary, patently unattractive minerals, used as a religious talisman and a good luck charm for centuries, be, in its transparent faceted form, a much sought after collector’s gem? Rarity! Seldom do…

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Let’s Talk Gemstones – Peridot

Peridot, often called olivine and chrysolite, is a gem variety occurring in the solid solution series between fosterite (Mg2SiO4) and fayalite (Fe2SiO4). The members of this most common solid solution series of the olivine group are the…

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Let’s Talk Gemstones – Zircon Group

Lets Talk Gemstones – Zircon is the single member of the zircon group of the nesosilicates that is suitable for use as a gemstone. In the nesosilicates, independent SiO4 tetrahedra are connected only by ionic bonds. Because the tetrahedra…

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Morganite – Pink Beryl

Richly colored morganite gems are among the more valuable of the secondary gemstones. The value of morganite has increased with the expanding knowledge of the gem-buying public. The more informed consumers become about gemstones, the more…

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Nesosilicate – Garnet Group

Garnet is a common mineral distributed worldwide. It occurs as crystals, in massive and granular forms, and as tumbled pebbles. It can form under a wide variety of geological conditions, but high temperatures are essential for its development.…

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Nesosilicate – Topaz Gemstone

Previous articles discussed the polymorph gemstones andalusite, sillimanite, and kyanite of the Al2SiO5 group of the nesosilicates. Topaz and staurolite are the two remaining minerals of this group used as gems. In the nesosilicate structure…

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Tanzanite – Zoisite

Tanzanite! Baron Sigismund Zois von Edelstein of Slovenia could never have imagined that a variety of the mineral he discovered in 1805 in the Sau-Alp Mountains would cause tremendous excitement in the jewelry industry more than a century…

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Uncommon Sorosilicate Gemstones

The sorosilicate class of minerals is composed of more than seventy minerals. Most are rare, and only a few are used as gemstones or are cut for collectors. The exception, the lovely tanzanite of the zoisite group that forms in the orthorhombic…

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Uncommon Sorosilicate Gemstones – Epidote group

With the exception of orthorhombic zoisite (tanzanite and thulite), discussed in the first article on the sorosilicate class of minerals, the members of the epidote group form in the monoclinic crystal system. Allanite, clinozoisite (the…

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Understanding the Different Beryl Varieties

The varieties of beryl found worldwide include one of the most prized and one of the lesser valued of gemstones. The now exhausted mines south of Koseir in Egypt provided Cleopatra with precious emeralds, including, reportedly, one engraved…

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Yellow-Green and Green Beryl

Yellow-green beryl has achieved ‘desired gem’ status with consumers just within the last few years. Museums were eager to acquire spectacular specimens, while connoisseurs sought it for their collections. However, fashion trendsetters…