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FREQUENTLY ASKED QUESTIONS ABOUT GEMS

 

     How do I tell if I have real Amber? 

     How are synthetic emeralds grown?

     Where are diamonds found in the United States?

     What is jade?

     What is the relationship between sunstone and labradorite?

    

How do I tell if I have real Amber? 

      One way to determine if it is real amber is by examining the physical properties. Amber is relatively soft (hardness about 2) so it should be easily scratched by a knife (glass will not scratch easily). Amber is also very light (density 1.05 to 1.06) so it will float in a salt water solution. Calcite will show a good cleavage and will also effervesce if a drop of diluted acid is placed on the specimen. Some amber does have a lighter shaded rind. This usually indicates that the amber has not moved very far from the tree that it originated on. The rind will be abraded off if it is found in a sandstone or gravel.
      There are several tests that can be run to determine if the material is amber, copal (a recent resin material) or a simulant.
One can make a salt water solution with 1 cup of water and 10 teaspoons of common salt. This will create a solution with a specific gravity of about 1.13. Amber, copal and styrene plastic will float in this solution, while other simulants will sink.
Disclaimer - do NOT use the following tests on a good exposed polished surface as it can mar the finish of the gemstone.
Benzole will dissolve styrene and not affect amber or copal.
Ethyl alcohol will soften copal after 30 seconds and not affect amber. Some portions of the surface can be rubbed off with a clean rag.
Ethyl alcohol for 30 seconds to 2 minutes will cause heated portions of amber in reconstituted amber to become opaque resulting in a mosaic structure.
A hot wire can be stuck into the specimen. If you get a resinous odor, the material is either copal or amber ( "pine woods scent"). Plastics will give a very bad smelling burnt plastic odor. 

     There was some amber from the Carboniferous and Paleozoic from fossil cordaites and cycadophytes, but the majority has been found in Cretaceous rocks. The major North American deposits are Alaska, Manitoba, and New Jersey.

How are synthetic emeralds grown?

Synthetic emeralds were first produced in 1848. Commercial production did not start until the 1940's. Chatham produced about 50,000 carats a year with about 10% being of gem quality. Crystal growing is more of an art than science with variable success rate. Presently there is production in the U. S., Japan, Australia, China, and Russia. Most of these producers either have patent protection or keep it as a trade secret.
There are two types of techniques that are used for the production of synthetic emerald. The main technique is called flux-melt growth. There is an oven which contains a heater to set up a temperature gradient and a platinum crucible which contains the source material ( beryl plus colorant) and a flux of a lithium molybdate or vanadate. Seed crystals are placed in the upper portion of the crucible. The apparatus is heated to about 800 degrees Celsius for a period of between 8 to 10 months.
There is also a hydrothermal process which uses an autoclave ( essentially a strong pressure cooker - it is also known as a bomb , for good reason). The crystals are grown at a temperature of 600 degrees and a pressure of greater than several ten thousands psi.
You may want to check out the science section on the Chatham website. 

Where are diamonds found in the United States?


       There was diamond production in Arkansas in the early 1900's. The Arkansas state geological survey web site gives some general information as well as specific information on the diamond mines in that state (The mine is open to the public as a state park - yes they do allow you to collect). Their web site for the Crater of Diamonds Park lists information on collecting.
       There has been production of diamonds from kimberlites near the border between Colorado and Wyoming. Many states have had occasional finds of diamonds in association with gold mining in California and the southern Appalachian mountains. There have been scattered occurrences in the north-central states in glacial deposits. These were primarily discovered  in the 1800's and early 1900's.
      The September/October 2000 issue of the magazine Rocks & Minerals has a short article on diamonds and another article on the Colorado diamonds. You can also find additional information in the Bibliography Section.

 

What is Jade?

     Jade is the gem name for primarily two minerals, jadeite and nephrite.

     Nephrite is fibrous variety of the amphibole tremolite( calcium, magnesium silicate). It has a hardness of 6 and a specific gravity of 3. The various colors include green, grayish white ("mutton fat"), blue and red. It has an oily luster.

     Jadeite is a granular pyroxene (aluminum sodium silicate). It has a hardness of 6.5 to 7 and a specific gravity of  3.3. The various colors include white, pink, lavender, yellow and green. The green varieties include emerald green or imperial jade, dark green - chloromelanite. It has a vitreous (glassy) luster.

     There are many minerals that can be confused with jade. The most common is green serpentine, but it is readily distinguishable by it's lower hardness. More difficult to determine are harder silicates such as massive vesuvianite ( variety "californite"), massive diopside, and massive green grossular garnet. Other possible minerals include massive zoisite, saussurite (zoisite or epidote and albite), smithsonite, prehnite, apatite, emerald, micas ("verdite"), steatite, chalcedony, aventurine quartz, green marbles, green porphyries, and fluorite. Glass and ceramics have sometimes been sold as jade.

What is the relationship between sunstone and labradorite?

Pete Modreski  replied

     The Oregon Sunstone is, in fact, labradorite.
"Sunstone" has been a loosely used term that has applied to a number of types of feldspar over the years. Although the books usually say that it is oligoclase feldspar containing hematite inclusions, "sunstone" has been used for any yellowish or golden-iridescent feldspar. And the sunstone now popular in the gem market from around Plush, Oregon, is indeed labradorite feldspar, not oligoclase.

     Although labradorite is best known for its common (actually, not all that common, rather it is the exception) form with a bluish, silvery, or multi-colored "schiller" iridescence, not all labradorite has that appearance. Most labradorite is gray, without the schiller, but some gem-quality labradorite is transparent pale yellow, with or without an iridescence. The Plush, Oregon labradorite "sunstone" is either clear yellow, orange, or red, and some of it has an iridescence which is due to microscopic inclusions of copper--something very unusual among feldspars, which was a surprise when its discovery was announced. Pale yellow gemmy labradorite is also found in New Mexico and Mexico.

     You can read about sunstone (from Oregon and elsewhere) on a "gemstones" publication online at the USGS website at:
http://minerals.usgs.gov/minerals/pubs/commodity/gemstones/sp14-95/feldspar.html

and also see informative web pages (with pictures) about Oregon sunstone at:

shttp://orerockon.com/Plush.htm
http://www.dustdevilmining.com/


Additional Gemstone Links

Gem Creation and Enhancement (Synthetics and simulants)

Gemology College Course University of Wisconsin

Gem Rocks by R.V. Dietrich

 

 


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