"Gemstones And How To Identify Them" 
by: Rexford Milhouse

 

[Assumed to be Page One since copyright is on it]
Gemstones 
and how to identify them 
[Sketch of diamond]
by Rexford Milhouse

©MDCCCLXXIII
[I believe this date would translate to 1873.]

Gemstones include any number of crystalline rocks which, when cut and polished, can be used as jewelry. Their commercial value usually depends on how rare they are, although beauty is certainly a factor as well. Because gemstones are, more often than not, found by accident, it behooves miners, prospectors, and even farmers to be able to recognize them, for the earth holds many natural treasures, but only for those who know what to look for. 

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Quartz
[Sketch of quartz to left of text] is one of the most abundant minerals on Earth. Crystalline quartz is a composite of six-sided prisms which have grown together in a process called twinning. Sometimes the crystals grow at the right angles to each other; but more frequently two crystals grow from a common prism face, or several crystals grow into each other so that the corner of one penetrates the face of another.

Amethyst 
is crystalline quartz that is lilac to deep purple in color. The deeper the color, the more valuable it is.[Photo of purple Amethyst to the right of text] 

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Citrine
[Photo of Citrine to the right of text] a form of quartz that is a rich golden color, is closely related to amethyst. In fact, if amethyst is heated to 550 degrees Centigrade, it becomes citrine, for the heat eliminates the impurity that causes its purple coloration.

Tiger’s Eye
[Photo of Tiger’s Eye to the left of text] is a fibrous type of crystalline quartz in which thin yellowish and reddish brown bands are apparent when light reflects off its polished surface. 


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Diamond 
[sketch of diamond]
is pure carbon, and is formed deep in the mantle of the Earth where extreme temperatures (more then 1000 degrees centigrade) and extreme pressure (50,000 times greater than on the Earth’s surface) make its crystal extremely compact and strongly bonded - hence diamond’s well known hardness. Due to their hardness, low quality diamonds have many industrial uses, such as for grinding wheels and drill bits.

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Magma brings diamond crystals to the Earth’s surface along with other rocks from the mantle. Thesekimberlite pipes often contains olivine (peridot), garnet and zircon as well as diamond. When gem hunters spot any of the indicator minerals pictured below, they would do well to search the surrounding area for diamond crystals. [Pictured below are Olivine, Zircon and Garnet]

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Tourmaline
[Sketch of tourmaline to left of text] comes in so many colors that it probably has, at one time or another, been confused with all the other stones in this book. However, tourmaline crystals are deeply and distinctly striated (grooved), prismatic, and triangular in cross section. The most common color is black, but some tourmaline crystals are multicolored, such as watermelon tourmaline, which is pink on the inside and green on the outside. [Picture of watermelon tourmaline on the right of text]

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Beryl
is a very diverse mineral with several gemstones varieties. Common beryl is an opaque, milky green, while its rarer gem varieties are transparent. All varieties form long hexagonal prismatic crystals which are similar to tourmaline crystals, but lack tourmaline’s characteristics striations. [Sketch of Beryl right of text]

Aquamarine
[Picture of Aquamarine to left of text] is the blue-green variety of beryl. While most gemstones form relatively small crystals, aquamarine has been known to form crystals weighting more than a hundred pounds, although such specimens are rare. 

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Emerald
[Photo of Emerald in center of text]
is a deep green variety of beryl which gets its color from trace amounts of Chromium. Emerald gemstones tend to contain extraneous matter; indeed, the source of a stone can sometimes be pinpointed by examining its impurities, or inclusions. 

Garnet 
is a relatively common gemstone. Because garnets often appear in their host rocks as almost perfectly faceted crystals, they [Photo of Garnet to the right of text]

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have attracted human attention for centuries. Unlike other gemstones, garnet forms relatively spherical crystals that are generally reddish in color and look somewhat like pomegranate seeds. 

Pyrope
[Pyrope photo to the left of text] garnet crystals are deep red. They form in the Earth’s mantle and are brought to the surface in much the same way as diamond crystals. Therefore finding pyrope increases the likelihood (but doesn’t guarantee) that diamond can be found in the vicinity. 

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Peridot
[Peridot to the right of text] is the most well-known form of Olivine. Its bright apple green crystals are thick and vertically striated, with wedge-shaped terminations and an oily luster. Most peridot is round amid basaltic rocks which have been brought to the Earth’s surface by lava. 

Corundum 
[sketch of Corundum to the left of text] or aluminum oxide, is the second in hardness only to diamond and, as a component of the black magnetic rock known as emery, has been mined and used 

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for thousands of years as an abrasive. Its crystals are commonly six-sided and barrel-shaped with tapering ends and are, when pure, colorless. 

Rubies
[Photo of Ruby to the right of text] are one of the two gem varieties of corundum. Rubies are deep red, and are formed when corundum substitutes for aluminum as corundum crystallizes. 

Sapphires
[Photo of Sapphire to left of text] include all the other color variations of gem corundum, and may be pink, yellow, green, blue, or colorless depending on which transitional elements (such as iron andtitanium)

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influenced the crystallization process. However, cornflower blue sapphires are by far the most sought after. 

Zircon
that is gemstone quality rivals diamond in it’s beauty and brilliance, though not in hardness. Zircon crystals are typically prismatic with pyramidal ends, and are usually found as single specimens. They may be suspended in rock or, because they are dense and durable, small grain-like crystals are often found in beach placer deposits. Natural gemstones are usually reddish brown, but when subjected to heat they turn yellow, colorless or blue. [Photo of Zircon to right of text]