On Gem Identification

Gem Related Discussion
1

Dear All,
There are a couple of questions I have in mind for quite some time :-

  1. We know that Scapolite is a positive stone and
    most others are negative. How are we going to
    make use of the optic sign property in gem I/D?

  2. When observing interference figures in crossed
    polars, must one use a strainless conoscope in
    this examination ?
    Denis

2

I’m not clear what you’re asking, but I’ll give it a shot

The optic character for scapolite is uniaxial with a NEGATIVE sign while quartz is uniaxial with a positive sign. Scapolite can be easily confused with quartz,
but quartz will usually show a bull’s-eye