Gem of the Month

Each month this section will feature either a topic of interest to gem lovers or one special gemstone with background on the material and its value.

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March, 2001

Fossilized Organisms as Gems

Most people who have an interest in gemstones or nature have seen petrified wood, fewer are aware of the many other types of fossilized organisms which can be fashioned into beautiful gems. Sometimes the whole organism is preserved as with Turitella snails, starburst algae or sea lilies. More often, though, various parts or products are all that has been preserved, such as bone, shell, eggshell, footprints or other impressions, tunnels or even dung. Usually the preservation occurs as the organic materials are replaced ever so slowly with mineral solutions, such as silica, which harden and take the original shape. In other cases mud in which the structure lies is compacted and compressed over time into shale which now holds the fossil. Sometimes as in the case of opalized clam shells a natural cast of the object is rendered in stone. Particularly beautiful are the ammolites which are the result of replacement of the thin layers of the shell of an ammonite (a snail-like extinct organism)with mineral layers which then create the phenomenon of iridescence.

Value:

With fossilized organisms, value is determined by basically the same general considerations that apply to all gems. Common items, like shark's teeth are generally inexpensive while rarer items like fossilized ivory or dinosaur eggshell command higher prices. In any given case, specimens which have the best patterns or most complete preservation of the organism in question are most valued
Gemological Data:

Makeup: varies, but often chalcedony, silicon dioxide

Hardness: often 7

Luster: often vitreous

Stones currently available:

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