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Stone identification

Hi all. I am recutting my moms old stone she had in a ring for 60 years. It’s been a daily wearer and the stone is in a remarkable good condition except the culet was a bit damaged. Probably the stone went in the floor after she had a replacement stone fitted. Anyway the stone was also really nicely cut and polished. Perfect meets my mom bought it as in Swedish bergskristall, clear quartz. First the stone was cut in quite shallow angles so I started to recut the pavilion to the same angles to fix the culet problem. It felt different to cut to other quartz I cut in the past, kinda hard. When I started to pre polish with 3000 on a batt it took quite some time and the stone got hot and also really shiny, normally when I use 3000 diamond on quartz it get pretty Matt . I never had that on quartz. When I tried to polish with cerium nothing happened. I went to diamond 60000 and it polished fairly nicely but I had to charge more then normal. So I put the stone with a dop on to the refractometer and used the old table and I got a reading on 1.73. I dunno if the dop making some problems with the reading but I can’t find any stone that fit to the description. I will finish cut the stone tomorrow and I can do a specific gravity test. But meanwhile any one have any idea what it can be. When I turn the stone or twist the polarization filter I only see 0 to very little difference.

Spinel? Natural or synthetic has an RI around 1.73, if thats any help.

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Greetings, check for spinel, Hardness is 8, which is greater than Quartz (7) and the RI you show is within the range for Spinel. Spinel also has cubic crystal format. You could look at my practical gemmology book at
Hope this helps. Adrian

Hi. I got the stone off the dop did some tests on it and everything indicates it’s a synthetic spinel.
Thx for your help.