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A very general overiew of gems and gemstones

Elvis Elvis

Lot’s of information to digest on this subject. Probably a few surprises for you – at least there were plenty for me!

A Gemstone is considered to be the finished product. Already cut and polished and ready for setting.

A gem is a mineral or other material used in jewelry and other purposes. Gems include diamonds, emeralds, opals, rubies and others we will discuss. An important thing to remember – there are certain standards and requirements for an item to be a true gem! For example, just because it is a diamond – it probably does not classify as a true gemstone. Very few diamonds mined pass the test. Research tells me that the richest diamond mines only produce @ 1 carat per 3 tons of ore mined! Many diamonds are of inferior quality and used for industrial purposes.

Gem minerals are the natural raw materials that are made or fashioned into gemstones primarily for there use in jewelry. We have received requests on information on identifying fake gemstones. It is not as easily done as you might think.

To conclusively identify some of these gemstones – an expert might be called to use chemical tests and even x-rays! Most gem minerals can be identified by their other properties:

Crystal shape: all like gem minerals should have the same crystal shape and symmetry.

Color: some variations are to be expected. Different gems may exhibit the same color. Too many variables to be an absolute measure.

Index of Refraction: a measure of how much a light ray bends as it passes from one medium and into another. The ratio of the speed of light in air as compared to the speed through the gem in question.

A very general overiew of gems and gemstones

(Beginning to see why it is so difficult for the average person to verify a stone?)

Cleavage: some minerals have a tendency to split in definite and repeatable directions often producing a flat surface. Cleavage is often confused with fracture – fracture produces uneven surfaces.

Hardness: very important factor in gemstones. Hardness (as rated by the Moh’s Scale) is a measure of how durable a gemstone will be. The scale rates from 1 – 10 with talc being a one and diamonds being a ten. A gemstone rated 7 or above would not easily be damaged by a steel knife blade or glass.

Specific Gravity: the ratio of the weight of a given volume of any substance as compared to an equal volume of pure water. Every gemstone has a certain expected specific gravity.

The quality of manmade and imitation stones is such that many professional jewelers cannot be certain. Even museums have been fooled. No easy answer on this one my friends. You will have to undergo extensive tests with equipment not readily available and possibly take a very real chance of damaging the stone to verify it! Acid tests, trying to scratch the stone with a stone of known value (lesser value) on the Moh’s Scale, x-rays, etc. It’s just not feasible for the average collector.

Below you will find links to pages discussing some of the most popular Gems/Gemstones. We hope you find them helpful.

Also – let me once again give credit where credit is due. Most of this information was derived from research with the U. S. Geological Survey and The World Book Encyclopedia. Both, excellent sources of information.

PS – I believe I have reached my limit on text links and am unable to add info on the Peridot Gemstone so I am including it here. All other major gemstone information can be viewed separately. Hope this is not an inconvenience.

Peridot – is a transparent gem. Because of it’s iron content – it almost always some shade of green. Peridot originates in a common rock forming material called olivine.

The higher quality peridot stones are often cut or faceted in various styles. The lesser quality stones are usually fashioned in the cabachon style or polished with abrasives in a tumbler.

Peridots have been found since Biblical times. The earliest source of peridot was Jazirat Zbarjad ( St. John’s Island).

Moh’s scale – 7.0 and specific gravity of 3.22 – 3.45.