Microlite Gem? 7.09carat?that's possible?

[clad]

Hello

I have this gem, after a few test with my gemology tools the result was this:
I never found a Microlite of 7.09 carat. I dont know if this can be possible.

RI index : 2.050
Specific Gravity : 5.61
Single Refraction
VVS / sparkling
Carat 7.09

Any help please

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[The Rock Hunter]

very nice stone sory have no idea not a facetor yet any way welcome clad to ALF     

[fossickeract]

   Man made cubic zirconia SG fits RI close microlite is descibed as microscopic translucent to opaque crystals although it does fit the SG and RI.

[Capt. Mendoza]

it certainly has a lot of fire...!

[clad]

Hello

before i make the test 3 gemologyst of more than 15 years of experience view this gem and all of the said that is not a cubic zirconia, the result was, they dont know (LOL).

Then i test the gem by myself, and i found that match with a rare gem earth (Microlite) in this site, there are many others.

http://www.realgems.org/list_of_gemstones/microlite.html

[fossickeract]

 Bit difficult to test the hardness but you should be able to find Na/Ca absorption lines using a spectroscope if it was Microlite. Also see it might be slightly radioactive!

[Findem]

I have to confess that I've never heard of a mineral called microlite. Perhaps it has been discovered since I studied mineralogy (many years ago). Where is it found?

[Lawrence]

I always love a good puzzle.

What method did you use to determine the RI?

What test did the gemologists perform to discount CZ?

Do you have a SWUV light source?

Man made Cubic Zirconia fits the data you have provided.

You mention VVS, what kind of inclusions can you see under magnification? Negative crystals, guest crystals, air bubbles?

Sadly, while microlite may fit, it is a long way from the most likely outcome, even heavily doped silica glass can fit the SG and RI.

[calxoddity]

I notice you haven't mentioned the hardness anywhere - what hardness is it?

[scratchie]

Calxoddity,
Re getting a measurement of hardness
Almost impossible to test a faceted stone unlss you're prepared to damage it a little
John

[chookie2]

Findem,
 Microlite is listed in Dana 1959 as being an ore of  tantalum, Microcline and albite- mainly found in Brazil apparently. Ca2 Ta2 O7. hardness 5.5.

[Findem]

Thanks Chookie. I see too that it's a pegmatite mineral. I should have consulted my Dana before commenting. 

[chookie2]

It seems that most good gems are originally from pegmatites- just how and where is the big question.