Hi everyone. I have recently bought several kyanite stones (1 carat per each gem). They are blue, sparkling. I took some pics of the inclusions under the microscope (x100). Here one of the gems
Under magnification I saw several parallel needles, I guess rutile inclusions (?)
Then I found this solid object, maybe a guest crystal (?)
What do you think about these inclusions? Thank you in advance
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
The needles appear to be rutile. The larger inclusion is impossible for me to ID from the picture. GemInterest.com has a large inclusion identified as staurolite on their site, but it does not really look similar to your shot.
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Rutile is listed as a common inclusion in kyanite. Sillimanite is a polymorph of kyanite.....same comp, different conditions of crystalization. Please explain your thoughts Scar. Not disputing, just unclear.
It's not too uncommon for any of the aluminosilicates to have taken multiple forms over their lifetimes, since their P/T conditions all fall within normal metamorphic ranges (hence why geologists love them so much--geobarometers are hard to come by.) So the chances of having some left over or some sort of pseudomorphing seem decent. Nothing profound or, if I'm honest, particularly informed, just a guess based on what I've seen in other samples and on how fibrous sillimanite usually is.
Thank you for your valuable considerations! I supposed the needles were rutile, since I consulted Geminterest. However, I found that the Scarodactyl's hypothesis is very intriguing... Regarding the 2nd crystal, I guess it's difficult to identify. I should observe it from different angles and in different conditions of light...
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Random neural firing: You know how it used to be thought that black inclusions in diamonds were carbon? Now we know that is incorrect because if the inclusions were carbon they would have altered to diamond during the xlization. I suspect the same with sillilmanite inclusions in kyanite.
Thank you for your suggestion, Marlow! I am new to gemology. However, I though that growth tubes were typical for tourmaline and aquamarine... But my knowledge is still very limited. Ciao!
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