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We have selected samples from C.I.G. 's comprehensive gem study collection which are difficult to identify. Most pictures were taken with an immersion-scope (methylene iodide or benzyl benzoate); under a common "dry" microscope with dark-field illumination many features shown here may not be visible. A detailed booklet with computer diskette containing over 100 micro-photographs is available from Gemlab Book Services . © 1996 J. W. Kuehn

Description of inclusion features have been provided by Peter G. Read

701Alexandrite, natural

702Alexandrite, synthetic

Synthetic alexandrite (fluxfusion): First manufactured in the early 1970s by Creative Crystals Inc. of Danville, Calif., this synthetic alexandrite has a colour change and characteristics resembling those of natural stones from Siberia.

Typical inclusions consist of a layer of dust-like particles parallel to the seedplate, and strong banding or growth lines. Some stones contain groups of parallel negative crystals. Unlike their natural counterparts, these stones have a high S.W. U-V transparency factor.

Seiko synthetic alexandrites have a swirled internal structure which is characteristic of the floating zone method of synthesis. These alexandrites have Verneuil-type tadpole inclusions (with long tails) and spherical bubbles. The colour change of these stones is reasonable, but not suspiciously good.