Monday, October 18, 2010

Mystery behind the chatoyant gemstone

"Chatoyance" is French for cat's-eye. When impurity minerals occur in fibers, they give gemstones a silky appearance. When the fibers line up along one of the crystalline axes, a stone can be cut to display a bright reflective line—a special effect called cat's-eye.

Pictured cat's eye chrysoberyl is also known as cymophane. The name being derived from the Greek words cyma and phanes, meaning “wave” and “appearance.” Microscopic needle-like inclusions inside the stone reflect a streak of light known as the cat’s eye.

The cat's eye’s inclusions are aligned parallel to the crystallographic axis and they are always cut as cabochons with the fibrous need-like inclusions running across the narrow part of the stone as this is the only way to display the effect properly.

Saturday, September 18, 2010

Alexandrite like phenomenal color change Garnet

Color change garnet is one of the most rare, interesting, and phenomenal of all gemstones. The color change can be intense and equal to the color change of top quality alexandrite and fine color change garnets can easily be mistaken for alexandrite. Some of the best stones are from the deposit in Bekily, Southern Madagascar. Stones from this mine are well known for their strong alexandrite like color change.

Change of color is not the same as the changes in color with crystal orientation that affects tourmaline and iolite, which are due to the optical property called pleochroism. Only rare tourmalines, garnets and alexandrite absorb certain wavelengths of light so strongly that in sunlight and indoor light they appear different colors.

Saturday, September 11, 2010

Alexandrite, Spinel and Diamonds Triple Eternity Ring

This triple eternity ring was initially created in the Victorian period. The meticulous engineering enables the interchangeable style to display a multitude of colors in a variety of combinations.

White gold alexandrite ring features red spinels from Burma, alexandrites from Brazil, and VVS diamonds from Africa. It can be worn as a single, double, or triple band and is ideal for special occasions or everyday wear.

Monday, August 30, 2010

Tuesday, August 10, 2010

Book Announcement: Russian Alexandrites

About The Book

In this book the author present an historical overview of emerald mining in the Urals, the discovery of Russian alexandrites in the Uralian emerald mines, the naming and historical use of alexandrites and their appearance and display in mineralogical museums and the gem trade. Morphology and twinning of rough alexandrite is described for single crystals, single contact twins and cyclic twins (trillings). Mineralogical and gemmological properties are thoroughly explained and numerous photo-micrographs of inclusions and growth patterns in faceted samples are presented.

Chatoyancy and asterism of alexandrite and chrysoberyl from Russia and Sri Lanka are also described. A further chapter deals with characteristic growth patterns of Russian, other natural and synthetic alexandrites. Colorimetric data of Russian alexandrites and green chrysoberyls are explained using the CIELAB colour space, and the distinction between these varieties is explained. A chapter on trace element chemistry and locality determination rounds off the book.

Book is illustrated with more than 200 colour figures and photographs, addresses mineralogists, gemmologists, historians, mineral and gem collectors as well as all members of the gem trade. An extensive appendix containing lists of historical names, a time table and numerous references provides valuable information on Russian alexandrites for all researchers in the mineralogical and gemmological fields as well as for gemmological laboratories, jewellers and gem dealers.

About the Author

Dr. Schmetzer is an independent gemmology researcher and consultant based in Petershausen, Germany, near Munich. He specializes in the mineralogy of gemstones, characterization of natural and synthetic gem materials, description of new gemstones and new gem localities, causes of colour and colour changes produced through treatment, and differentiation of natural gemstones from their synthetic counterparts.
As prolific author, Dr. Schmetzer has produced nearly 400 papers and articles, mostly in English and German, which have been published in the major gemmological journals, including Gems & Gemology, Journal of Gemmology, Neues Jahrbuch fur Mineralogie Monatshefte.
He is a member of the editorial board of the American, Australina, and French gemmological journals. He has been invited to lecture at special gemmological conferences in the United States, China, Brazil, Austria and Switzerland, and he is the German delegate to the International Gemmological Conference.

For more information, please visit Book Announcement: Russian Alexandrites by Karl Schmetzer