Opinions on a stone....Gemologists opinion welcome

[RockHugger]

I purchased a santa maria aquamarine. I received it and popped it on my refractometer, and it is refracting at 1.61 (topaz) but the birefringence is only .004 (beryl, topaz is .008-.016). So I am beyond confused. I popped some topaz in to compare and the topazes all have the typical high birefringence.

Ideas? Are there any other stones with the same optical properties I am missing?

 

[Michael_E]

I think that you've got a topaz. Aqua is almost always below 1.6 and usually in the 1.57 to 1.58 range for R.I. Topaz is also significantly more dense with an S.G of 3.53 or so with aqua being much lower at 2.72, ( a very easy separation). These stones also have different optical characters if you've got a polariscope to test that. How did you measure birefringence that accurately? I still have my one and only "Santa Maria" topaz. I keep it to remind myself to test things before putting out significant money. "Santa Maria" topaz is pretty too, hope you didn't pay too much!

 

[RockHugger]

I think your right. I just measured SG and it is a topaz. I am returning it this afternoon. I paid a decent sum for it, but I can return it. The man who sold it to me had a digital refractometer, and he showed me the dig saying it's beryl.

My refractometer has a filter and little tiny lines that measure .001.

Shows how reliable those digi refractometers are.

All my aqua test at about 2.76, give or take a .01 due to my super thin silver wire.

 

[digitaldevo]

Another way is pinch the stone between your fingers. If it is slippery then it is topaz more then likely. Easiest way to separate topaz from any other stones really. Topaz will always be almost greasy and slip out very easily with little resistance. Go ahead and laugh, but look it up, it is a valid and reliable testing method, great for field work. . Learned it from Bill Hanneman's writings.

 

[Edward Bristol]

True, topaz is slippery stuff, old jungle dealer trick.

 

[chrono]

RH,
Did it turn out to be topaz after all? I know you are returning it but wondered if you had the chance to try the slippery test.

 

[RockHugger]

Lol it's no more slippery then any other stone. But the sg is way off for beryl.

 

[digitaldevo]

In all seriousness. If you hold a known topaz in one hand and say a quartz in the other or even beryl and pinch them both at the same time the topaz will always act like it is covered in grease and slip out far more quickly and easily then the other stones will. It is an old field trick for making sure folks aren't trying to pass topaz off as aqua and stuff like that.

 

[RockHugger]

Well the stone doesn't act like that at all......weird little bugger. It doesn't slip like it's greasy.