Peridot
In mineralogy, the name olivine is used.
Physical properties:
| Chemistry: | (Mg, Fe)2SiO4 |
| Hardness: | 6½–7 |
| SG: | 3.25–3.45 |
| Cleavage: | Imperfect, 1 direction |
| Fracture: | Somewhat brittle |
| Heat sensitivity: | Low |
Optical properties:
| RI: | 1.65–1.69 |
| Dispersion: | 0.020 (medium) |
| Double refraction: | 0.036 (medium) |
| Pleochroism: | Weak |
| Critical angle: | 37° |
Facet angles (pavilion/crown):
| Vargas: | 42°/41° |
| Olson: | 40°/43° |
| Soukup: | 39°/43° |
| Roth: | 39°/43° |
| MDR: | 39°/43° |
| Schlagel: | 39°/35° |
| Hashnu: | 42°/41° |
| Sinkankas: | 40°/40° |
| GIA: | 40°/42° |
| Perkins: | 39°/43° |
| Raytech: | 40°/39° |
| Cornwall: | 42°/35° |
| Weikoff: | 42°/39° |
| Carroll: | 42.4°/35.3° |
Cutting lap:
Medium to fine
Facet polishing:
| Vargas: | Aluminium oxide on tin/lead, Tin oxide on tin, Cerium oxide on acrylic |
| Olson: | Aluminium oxide or diamond on tin or wood |
| Soukup: | Tin or aluminium oxide on tin or tin/lead |
| Christiansen: | Aluminium oxide on tin/lead or tin, Cerium oxide on acrylic, Diamond on tin or wood |
| Perkins: | Aluminium oxide on BATT or Corian |
| Raytech: | Aluminium oxide on Fast Lap, tin or phenolic |
Cabochon polishing:
| Christiansen: | Aluminium oxide on leather, Diamond on leather or wood, Cerium oxide on felt |
Orientation:
According to shape and yield
Treatments/synthetics:
The only treatment that peridot undergoes is rarely encountered oil or wax impregnation.
Tips!
It can be difficult to polish. Many add formic or acetic acid to the water during polishing. Diamond on tin is described as a "patent solution" from several sources.
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