Semi-Precious Stones and Gems

In the early days of cinema, many movie stars wore their own jewels in their movies. Some of the stars sporting their very own rocks "onstage" were Merle Oberon, Marlene Dietrich, and Gloria Swanson.

The Mohs Scale of Mineral Hardness was composed in 1812 by German mineralogist Frederich Mohs, who listed 10 common minerals in order of hardness. The word "hardness" here is rather misleading, however. They're really ranked in order of scratch-resistance or toughness, with the most easily scratched (talc) at #1 and the hardest to scratch (diamond) at #10. A mineral with a lower number on the scale can be scratched by any of the minerals with higher numbers. Talc can be scratched by anything on the list, while - technically, at least - only another diamond can scratch a diamond. A lot of other factors go into the actual hardness of a stone, however. Some with relatively high Mohs ratings are actually quite brittle and will break with very little effort. So it's always best to treat your stones with respect, no matter what they happen to be rated with Mohs!

The List, numbered according to hardness, follows. (Items in parentheses are not on the list, they're just there to help lend "scale.")

1. Talc - the world's softest mineral, talc is used in a variety of products. You probably know it best as talcum powder and an ingredient in most powder makeup.

2. Gypsum - Used in plaster, plaster of Paris (what they make casts for broken limbs of), drywall, and modern day blackboard chalk (which used to be actual chalk, which is slightly softer, I believe).

(2.5 - Fingernails)

3. Calcite - One of the most widely dispersed minerals on earth, calcite is found in crystals on its own, as well as in seashells, limestone and other sedimentary rocks, and peridotite (of which olivine and peridot are members).

(3.5 - A *copper* penny)

4. Fluorite - A pretty crystal stone in its own right, fluorite also has several industrial uses, including lens elements in high performance cameras and telescopes.

5. Apatite - A pretty gem, apatite was also once used in fluorescent lights.

(5.5 - Window glass)

6. Feldspar (orthoclase) - Feldspar makes up a full 60% of the earth's crust. This abundant mineral is found in most rocks and is an ingredient in porcelain. It's also the state gem of Florida.

(6.5 - Steel file)

7. Quartz - The single most abundant mineral in the earth's crust, quartz is found just about everywhere and is in most everything. Amethyst, citrine, and chalcedony are all forms of quartz. It's one of my favorite rocks.

8. Topaz - Topaz comes in a variety of pretty colors, in blues, pinks, greens, and yellows, as well as clear. It may be heat-treated, so buyer be wary and pay accordingly.

9. Corundum - AKA sapphires, rubies, and padparadschas (pinkish orange sapphires), pure corundum will leave a streak of white behind when used to scratch nearly every mineral below it on the scale.

10. Diamond - The hardest natural mineral known, diamonds come in all sorts of colors, including blue, green, yellow, pink, and red - not to mention brown. They are graphite's prettier, dressier sister - you might want to feel sorry for your pencil lead the next time you make out your grocery list. . :)

This translucent stone, very similar to aquamarine in color, is actually blue topaz, the birthstone for November, and the state gemstone of Texas. It carries a Mohs rating of 8, and despite its name, occurs in a variety of colors in addition to blue, including orange, green, pink, and red. Blue topaz is often irradiated to produce the shades of blue for which it draws its name, Sky Blue being the lightest and London Blue the darkest, with Swiss Blue falling between the two. One of the most widely used and popular gemstones, blue topaz occurs naturally across the globe and is found in Africa, Brazil, Sri Lanka, Burma, Russia, Japan, Australia, Tasmania, Pakistan, Mexico, and the United States. It is believed to stimulate the throat chakra to enhance communication.

Green is the color most often associated with this beautiful, generally opaque stone, but it's also found in lavender, orange, black, & many others. In fact, the stuff we call jade is actually 2 different minerals: jadeite and nephrite. Nephrite is actually a form of actinolite very different from that of other varieties of the mineral. Oddly enough, it was almost 4,000 years before the discovery in 1863 that what everyone was calling by the single name of jade was actually 2 different stones. Since the 2 had been in use for roughly the same amount of time, everyone decided to just keep calling both jade. But the Chinese, who called nephrite jade, designated jadeite as "new jade". Today many collectors still use the terms "old jade" and "new jade" to refer to nephrite and jadeite, respectively.

Jadeite is rather rare and considered by many collectors to be the true jade. The most expensive & desirable jadeite comes from Myanmar and is often called Burmese Jadeite, Burma Jade or Chinese Jade. The most valuable form of jade, Imperial Jade, also comes from Myanmar. Deposits of nephrite in British Columbia have produced gem-quality green stone sometimes called British Columbia Jade. And small deposits are found in Australia, which also mines the green chalcedony sometimes referred to as Australian Jade.

Several other stones are often misrepresented as jade. Unscrupulous sellers label green aventurine jade, and chrysoprase, with its vibrant greens, is often labeled jade or Australian Jade, but is truly the most valuable form of chalcedony. South African or African Jade is really lush green grossular garnet hard as jadeite & also called Transvaal Jade. Other stones are more and more often labeled as jade but are not truly any form of the rock. These include Malaysia Jade: translucent quartz which has been permanently dyed and may be called by its color (ie. yellow jade), Mountain Jade: opaque dolomite marble from Asia also dyed in vibrant colors, & various forms of serpentine. One light green form of serpentine is often called New Jade, but is not jade at all. Careful, scrupulous dealers will label these false jades as "Jade," but do not assume this to be the case. When purchasing jade, it is always best to shop from reputable dealers and ask!

Jade is an incredibly durable and tough stone, rated from 6 - 7.0 on the Mohs scale, with jadeite the harder mineral of the two, and the "dividing line" at 6.5.

A recent Google search for "african turquoise" turned up 9,760 sites selling jasper beads, jewelry, or other ornamentation, and of those, easily 90% or more of the links I clicked misrepresented the stone as real turquoise, either out of mistaken belief that it is, or because they're trying to capitalize and make money fraudulently off of the name. A search for "african turquoise jasper" turned up a mere 2 pages of finds, and of those, at least 2 sites were there because of the proximity of the words "african turquoise" to the word jasper, not because the stone was appropriately identified as jasper.

Though it is a lovely stone and an aesthetically pleasing substitute for the real deal, African "turquoise" isn't turquoise at all. It's actually a very common rock called jasper, completely unrelated to turquoise. Jasper is a member of the quartz group and ranges from 6.5 to 7 on the Mohs scale, making it a somewhat sturdier rock than turquoise, but it is still far less expensive, and while african turquoise jasper is an acceptable substitute for actual turquoise if all you are concerned with is appearance, the difference in stones should certainly be reflected in a much lower price for jasper.

You can see more images of turquoise jasper in the turquoise imitations section further down the page.

One of the most rare opaque jewelry minerals on earth, turquoise made its way to Europe as a trade item from Turkey during the Crusades. It gets its name from the French word for Turkish and its bright blues from copper, though it is also found in bright green, when chromium is also present. Rated a 5-6 on the Mohs scale, it is easily damaged from hard contact, so extra care should be taken with your turquoise jewelry. Because turquoise is so rare, not much of it is allowed to go to waste. As a result, there is a grading system for the stone:

Natural turquoise is untreated, rare, and very expensive, making up less than 3% of all turquoise on the market worldwide. Most stone of this grade carries the name of the home mine and is distinctive to the veins of that particular mine; Carico Lake Turquoise is one such example, although some named turquoise may also be stabilized.

Stabilized turquoise is softer turquoise which has been injected with clear resin during a process using heat and high pressure, to make lower quality stone harder and more durable. The colors are natural and permanent, and stabilized turquoise may also be polished.

Treated turquoise is similar to stabilized turquoise, but the resins injected also contain dye. This color is permanent but not the natural color of the stone, and may look artificial. The price for treated turquoise should be lower than that of natural or stabilized turquoise. A great many beads and jewelry items on the market today are stabilized or treated turquoise, as this allows for more affordable items.

Reconstituted turquoise is comprised mostly of very soft "chalk" turquoise and scrap which have been ground into powder, then mixed with blue dye and plastic and molded into blocks or cakes which are subsequently cut into desired shapes or bead forms. A great many heishi beads are of block turquoise. In my opinion, reconstituted or "block" turquoise is little more than simulated or imitation "stone", and should not be sold as the real thing, though a great many dealers will do so. If you will buy reconstituted turquoise, please at least do so when the quality is adequately reflected in the price.

Imitation turquoise is comprised of turquoise lookalikes such as glass, plastic, clay, or dyed howlite. A great deal of stone represented in the marketplace today as turquoise is actually dyed howlite.

In addition to the five official grades of turquoise listed above, there are other treated forms of the stone on the market today. These include Enhanced turquoise - turquoise which has been impregnated with quartz via man-made process, will take a high polish, and is hard to distinguish from natural turquoise, which may also contain quartz - and wax-treated or sealed turquoise.

Much of the turquoise coming from China has been wax-sealed to deepen and stabilize the color. The treatment affects only the surface of the stone and is not permanent. Sealed turquoise has been surface sealed with an epoxy or resin to protect the stone from color change due to dust, chemicals, and skin oils from seeping into the surface of the stone. It is long-lasting, but not permanent, and some color change is inevitable.