I was wondering if someone could help me out. I’m kind of stuck trying to identify these two gemstones. We got these online from lord knows where last year. I’ve finally gotten around to checking them and I have no idea what they are. At first, I thought they might be glass/past but they’re doubly refractive, so I guess that rules glass out.
It is doubly refractive.
This one has a SG=2.58
min IR value of 1.518
max IR value of 1.521
Birefringence as I calculate it at +.003
reacts very weakly to SWUV and inert to LWUV.
Bloody hell this is a hard one. My copy of Gemology Tools Pro doesn’t have any solid matches (2014 edition). I am having to go off of my limited experience.
Bottom stone Has coloration similar to amazonite, however is significantly more transparent than is typical.
RI 1.522-1.53(near miss)
SG 2.56-2.58(match)
Double refraction
Birefringence does not match (0.021 or .0008. Both values are given in different locations on IGS)
Color on the top is similar to most Grandidierite I have seen.
However the numbers don’t match.
Low SG on a Grand is 2.85 with RI being a bit high.
And all of the other lovely near misses
-Albite RI is 1.528-1.533(miss) SG is 2.6(near miss)
Color matches
-Carletonite RI 1.517-1.521(match) SG 2.45(miss).
Color does not match
-Cancrinite RI 1.5-1.53(match) SG 2.42-2.51(miss)
Color does not match
Bottom stone has a blue green color similar to some emeralds/beryls out of Montana. but once again values are off.
Both colors are also seen in Apatite. Values all over the place, being variable based on composition. Really not happy with this answer.
While I am almost certain none of this helps you with your identification, hopefully it will serve others as they conduct their own research into what these may be.
I will continue researching until someone picks up the torch.
@rlynch Thank you for taking the time to look up my measurements and responding. These two gems have been festering in the back of my mind for some time now. They were sold as tourmaline, but the values don’t match and I can’t figure it out with my rather limited experience.
I created a spreadsheet with all the values for RI and SG and birefringence to help me figure this one out and I am completely stumped. I got the values for the spreadsheet from IGS, and other websites as well as some gemology books I own (this took me a very long time to complete). My measurements can’t be that off since my values match corundum and quartz very accurately. (I’ve bought synthetic gemstones to help me build a synthetic to natural comparison library, and my measurements of these gems are well within the values in the various gemological books I have as well as the information available on the internet).
I was thinking of purchasing gemology tools as well as a windows emulator since my spreadsheet didn’t help me figure this one out at all. I have no idea out what it is… let alone if it is a synthetic or a natural gemstone. I do have a spectrometer, but I haven’t figured out how to use it reliably yet. Perhaps that could help me identify the stone, but I don’t have much time for studying and running my various businesses.
AT this point, a chemical analysis might be the most prudent option.
Or sending to one of the major labs.
Alternatively, browse through https://www.gemrockauctions.com/ to see if you can find anything that matches your stones in color. Then run whatever they are through your spreadsheets to see if you get a match to what you have.
Top stone seems to show conchiodal fracture lines at the bottom right. And it seems to display an orange “fingerprint” top center. The fingerprint was reminiscent of sun-stones. While a google search turned up blue sunstones, they all look like blue goldstones ruling out both possibilities.
While it is possible for these stones to be synthetic, its highly unlikely that they are. There is no financial gain for synthetics to look anything less than pristine unless someone is trying to replicate a highly desirable stone. Tourmalines or anything outside of the big three (diamond, beryl, corundum) simply do not warrant the expense of engineering inclusions into the stone to make them appear more natural.
Now it could be that they are rejects from a failed batch that someone used to practice cutting on. But still seems unlikely.
What color is their UV reactance? And what are their sizes? That may help point me in directions I haven’t thought of before.
I bought some big stones similar to that one on ebay. They were advertised as emeralds. I new they weren’t because they were 20 dollars for two big stones but i wanted to see what they were selling. After several tests i concluded mine were quartz. They matched all the numbers and the inclusions looked like quartz.
Have you measured their hardness (Mohs scale)? Knowing that should at least rule out certain possibilities.
I’m surprised that people who ask for help with identification haven’t done a Mohs hardness test. It’s really simple: If it scratches quartz, then it’s hardness is >7. That rules out any feldspar mineral, for example. Ruby and sapphire have a hardness of 9, so if a sample of corundum (chemically, it’s aluminum oxide, same as rubies and sapphires) cannot be scratched, then the sample hardness is < 9. If it also scratches quartz, then its hardness is between 7 & 9. Most likely a mineralogy reference book would call it an 8. Look these tests up in a mineralogy book; a book intended for collectors and amateurs should be adequate. There are also kits of small spikes made of materials with well-known hardnesses that you can use.
I may be out of touch with new ideas about identification, but I never recommend testing for hardness on a cut gemstone. A scratch (even on the back in the pavilion) will decrease the value of the stone and often will show up when viewed at different angles through the crown. I would send it off for a chemical analysis well before I would be so anxious to know its ID that I would scratch it. Of course I do faceting as well as gem collecting… so my viewpoint is a bit different.
You can use the gemstone itself to try and scratch a piece of quartz. If the stone can’t scratch quartz then it’s probably not going to matter. On that note, I agree with you… don’t scratch your stone, that’s not a good idea. For 250 you can buy a presidium gem tester and it will narrow it down for you too.
I retested it and used gemology tools pro to help whittle down the possibilities. I can’t help but admire this little but of software. It has inclusion galleries built into it as well as a neat little tool to find possible matches to your readings. It’s a fantastic tool i should have gotten much earlier.
I had to rerun the specific gravity with a digital scale and not an analog one.
I ended up buying a digital balance that is specifically designed to measure specific gravity.
It turns out that my SG readings were off using the analog scale and so we’re my RI readings… The revised ones coincided with iolite within the margin of error for iolite.
Iolite is so strongly pleochroic with a dark blue direction, that I am suspicious that you made the ID. Also in response to Trevor’s comment about trying to scratch quartz; hardness is a funny property in that if you can’t scratch the quartz, then it means the quartz is scratching your stone… and you are probably losing that sharp facet corner that you used for your hardness test. Again, I repeat, I highly recommend that you do not use the hardness test when trying to ID your gemstone
So, is the final conclusion really that it’s Iolite??? I can’t bring myself to believe that! It’s almost green, and I have never laid eyes on Iolite that is remotely green… Where’s the dichroism???
