Incredible gemstone stories

Everybody who has worked for a certain time in the gemstone business will hear these incredible stories sooner or later. Incredible are the number of variations and also the insistence of the people telling them.

I can separate Topaz and Aquamarine by the naked eye.

I have heard this sentence many times. Only I cannot do this by the naked eye, or only with a portion of doubt. Usually I measure the refractive index. It is also possible to measure the specific gravity, or a chelsa filter will give some clues.

Pale blue stonesRefractive indexsepecific gravity
AquamarineRI 1.577 - 1.583 2.67 - 2.71
TopazRI 1.610 - 1.6383.53 - 3.56
Spinel and
synthetic Spinel
RI 1.712 - 1.7363.58 - 3.61

In addition, light blue synthetic spinel's appear perfectly identical to the eye as topaz or aquamarine. The synthetic flame fusion spinel's are recognized with the polariscope due to the tension related false double refraction. Natural and synthetic spinel's are otherwise identical in composition and optical properties.

Pale blue stonesChelsea FilterInternal tentions
Aquamarinegreenish blue to pale bluenone
Topazpale yellowish to colorlessnone
Synthetic Spinel
flame fusion by Verneuil
pale pinktentions or internal strains
Flux grown Spinel none
Natural Spinelno reactionnone

The results of the Chelsea filter are not conclusif and need to be confirmed with an other test.

To rely on color only, for the determination of precious stones, is risky. I prepared a set of gemstones and invite you to test yours skills. This set is at your disposition for visual inspection at the following mineralshows.

Take a chance and test your self
Stone 1
Stone 2
Stone 3
Stone 4
Stone 5
Stone 6
Stone 7
Stone 8
Stone 9
Your name

Hubert Heldner   April 2004



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