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The Flowers of the Kingdom
By Sandra I. Smith   
Rated "G" by the Author.
Last edited: Tuesday, February 06, 2007
Posted: Tuesday, February 06, 2007

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Flowers of the Kingdom describes how minerals combine to form gemstones.

The Flowers of the Kingdom
By Sandra I. Smith


Do you know what diamonds, rubies, and emeralds are? "Jewels" is the answer most people offer. It's an accurate answer, but it doesn't tell the fascinating story behind these treasures from nature.
Jewels are the end result of a process begun billions of years ago when the Earth was first formed. All that existed originally were the elements. Common elements you may be familiar with include oxygen, silicon, and carbon. Gold and silver are also elements. Far below the Earth's surface, where they were subjected to tremendous heat and pressure, certain elements combined to form minerals.
Atoms of an element may combine with other atoms of the same element; or they may combine with atoms from other elements to make compounds. Sulfur is a pure mineral, that is, it contains only sulfur atoms. Sulphur atoms may also combine with iron atoms to form a compound mineral called pyrite.
Minerals, and substances made from them, all belong to the mineral kingdom, which includes more than 3000 members. Approximately 100 minerals are classified as gemstones. Although a few gemstones are used for industrial purposes, most have value solely to collectors. Only about a dozen gemstones are suitable for use in jewelry.
Due to the exquisite way in which most gemstones crystallize, they were described as "the flowers of the kingdom" by Abbe Hauy, an early French crystallographer.
Diamond, which is pure carbon, is the only gemstone formed from one element. All the other minerals that we classify as gemstones are compounds--they are minerals that include atoms from more than one element. Because the elements that combine to make minerals are chemicals, gemstones can all be described by formulas. For example, quartz is a combination of silicon and oxygen called silicon dioxide. It is written as SiO2.
A gemstone's chemical composition determines its appearance. Although they are both blue stones, sapphire and turquoise look and feel entirely different. That's because sapphire is an aluminum oxide (aluminum and oxygen) with a trace of titanium, while turquoise consists of aluminum, phosphate, and copper. Ruby is an aluminum oxide like sapphire, but a trace of chromium replaces the titanium and makes rubies red, rather than blue.
Another important factor affecting the appearance of gemstones is the way in which the atoms are bonded together within the stone. Diamond and graphite both are pure carbon and have identical chemical formulas. However, they are entirely different substances due to the way the carbon atoms in each fit together. Carbon atoms in diamond crystallize in a tightly-bonded regular pattern. The same atoms in graphite form scales or irregular masses, which makes it soft and slippery.
Three criteria distinguish the flowers of the kingdom from other minerals: their beauty, rarity, and durability.
Beauty in gemstones, like everything else, is a matter of personal taste and changing fashions. The beauty in some gems, like turquoise, is based on color alone. In others, the color is secondary to the brilliance, or "fire," such as with diamonds, the most prized of which are colorless. A variety of colors in one stone, such as the green stripes in malachite, appeal to many.
Gemstones that are hard to find are valued more highly than those that are abundant. Treasured for its changeable colors, alexandrite is also valuable because it is so rare. Very little natural alexandrite exists. Although they are both glorious reds, rubies are prized more than garnets, because nature made a lot more garnets than she did rubies. Other gemstones, although seemingly abundant, yield only a few specimens that are of usable quality. Gem-quality opals are difficult to find and very expensive. Common opal is abundant and inexpensive.
Many rare and beautiful gemstones can't be used in jewelry because they aren't durable. They disintegrate or break too easily. To be durable, a stone must be stable, tough, and hard.
Stable gemstones remain unchanged by heat, light, or chemicals. For example, strong light can cause yellow topaz to fade. Gems, such as opals, that consist partly of water will dehydrate (dry out) and possibly crack if placed near heat or under strong lights. Malachite and rhodochrosite, which are carbonate-based, can be ruined by contact with acid solutions. Skin oil and perspiration are strong enough to cause discoloration in turquoise. Because of their beauty, these unstable gemstones are often used in jewelry, but they must be stabilized in some way first or placed in a setting that will protect them.
Toughness refers to the brittleness of a gemstone. The more brittle it is, the easier it will break. Jadeite and nephrite (the two jades) are the toughest, or most difficult, to break. Rubies and sapphires are also very tough. Diamond, the hardest substance known, is very brittle and will easily shatter.
Hardness, which is different from toughness, is the ability of a gemstone to resist scratching and general wear. Gems are usually rated on their hardness according to the Mohs scale, developed by mineralogist Friedrich Mohs in 1812. (Mohs rhymes with nose.) The Mohs scale ranks minerals from one to ten, with one being the softest and ten the hardest. Most of the commonly used gems have a Mohs hardness of 6 or greater. Window glass has a hardness of 5 and may be scratched by most gemstones. A steel file will put a scratch in all gemstones with a hardness of 7 1/2 or less.
Following is the Mohs hardness of some common gemstones. Amethyst and tourmaline are rated at 7, while emeralds and aquamarines are slightly harder at 7 1/2. Peridots are 6 1/2. Moonstones, opals, and turquoise all have a Mohs hardness of 6. Lapis lazuli is softer at 5, but harder than malachite, 3 1/2 and chryscolla, 3. The organic gemstones, such as pearls, amber, and coral, are the softest. (Organic gemstones, which are formed from living substances, are not members of the mineral kingdom.) Glass imitations of gemstones are usually Mohs 6 or less.
Quartz, which is ranked at 7, is the most common of all minerals and is a component of many gemstones, including amethyst and rock crystal. Quartz is found in rocks, dirt, and sand, all of which form dust. This means that most dust contains particles of quartz, giving dust a Mohs hardness of 7. Dust can scratch nearly all gemstones. Consequently, never rubbing dust off any gem when cleaning it is very important.
Gemstones usually go to a lapidary after they are mined. The lapidary does the final cleaning, which may involve grinding off the matrix, or rock, in which the gemstone was buried. While some gemstones may be simply polished, most are cut. The softer ones, like turquoise, are usually cut in rounded shapes called cabochons. Cabochons were the only way in which stones were cut until about the 14th century, when faceting was developed.
Only the harder gemstones can be successfully faceted. Faceting is the process of cutting a gemstone to improve its beauty by making it reflect more light. A faceted stone has had all rounded and uneven surfaces cut into flat "faces," which are highly reflective. A gemstone that has been cut and polished is called a gem, or jewel.
People who study gemstones and gems are called gemologists. Gemology is a relatively new field that began as a speciality of mineralogy. Gemologists must understand mineralogy, crystallography, physics, chemistry, and geology. As more synthetic, enhanced, and imitation gems become available, gemologists must also acquire the knowledge and equipment necessary to distinguish fake from real.
The flowers of the kingdom have captivated people since prehistoric humans first picked up shiny stones from ancient streambeds. These dazzling treasures from nature, eons in the making, are today crafted into jewelry of timeless beauty.
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