Thanks Mike, very quick reply:-)
Im new to your site , still trying to navigate my way around.
I was trying to add a bit more info as my initial thoughts were quartz, however, I took the Gem for testing (a Presidium Gem tester was used) and it came Back as Spinel! I was over the moon! As did not have a large specimen like this in my collection, this crystal measures approximately 8cms in length and approximately 2cms width with a weight of around 45grams.
Ive been an avid collector and enthusiast of Rocks and Minerals for years, cant go anywhere without bringing samples back to further examine and admire.
So my ultimate question is how accurate is the Gem tester that we used?
We tested the upper Table of this magnificent Gem, where it seems to be eye clean to limit a false reading from inclusions etc, So I am totally confused! We tested the equipment by using Known Corundum Rough Prior to testing this piece also.
Ive done quite a bit of research into spinel since but all information I can find indicates that Colourless/white Spinel is very, very rare~Especially Natural, which this appears to be. Ive included a birds Eye View of this twinned Crystal as previous pictures are very obscure.
I thoguht your original question was a little terse!
I am not familiar with your test equipment, but in general:
- such things are only as good as their operator (if that)
- most mineral species are variable to some extent, which increases the chances for misidentification.
My feeling is still quartz; spinel tends to be more regular in its crystal faces (different crystal systems).
...And as you rightly say, a nice clear specimen like this would be rather rare if spinel.
Spinel and quartz have several technical similarities, but one easy one you can use to discriminate is density.
Spinel is ~3.6-4.1g/ml; quartz is 2.65g/ml.
You have a nice solid specimen (without cavities and disinclined to absorb water), so you will be able to measure its volume accurately using the water displacement method. Then, once weighed (more accurately than 'about 45g'), you can calculate its density.
Let us know!
- spinel - http://www.mindat.org/min-3729.html
- quartz - http://www.mindat.org/min-3337.html
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