Pyrope
One of six end members in the garnet family. Pure pyrope does not exist; a certain proportion of almandine and/or spessartine is always mixed in. To be classified as pyrope, SG should be <3.93 and RI <1.77 (there might be variations in the limit values depending on the source). The properties below are given for the entire pyrope group, but to distinguish the classic "standard pyrope," its values are indicated in parentheses. Chrome and pastel pyropes have slightly lower values.
Physical Properties:
| Chemistry: | Mn+23Al2(SiO4)3 |
| Hardness: | 7.25 |
| SG: | 3.65–3.93 (3.80–3.93) |
| Cleavage: | None |
| Fracture: | Sometimes slightly brittle |
| Heat Sensitivity: | None |
Optical Properties:
| RI: | 1.72–1.77 (1.75–1.77) |
| Dispersion: | 0.026 (medium) |
| Double Refraction: | None |
| Pleochroism: | None |
| Critical Angle: | 35° |
Facet Angles (Pavilion/Crown):
| Vargas: | 41°/40° |
| Olson: | 39°/37° |
| Soukup: | 42°/37° |
| Roth: | 42°/37° |
| MDR: | 42°/37° |
| Schlagel: | 40°/36° |
| Hashnu: | 41°/39° |
| Sinkankas: | 40°/40° |
| GIA: | 42°/37° |
| Perkins: | 42°/37° |
| Raytech: | 40°/38° |
| Cornwall: | 41°/34° |
| Weikoff: | 42°/39° |
| Carroll: | 42.1°/35.3° |
Cutting lap:
Medium - fine
Facet Polishing:
| Vargas: | Aluminum oxide on tin/lead, tin oxide on tin |
| Olson: | Chromium oxide on tin |
| Soukup: | Aluminum oxide on tin or tin/lead |
| Christiansen: | Aluminum oxide on tin/lead, tin oxide on tin |
| Perkins: | Aluminum oxide on BATT or Corian |
| MDR: | Tin or aluminum oxide on tin, aluminum oxide on type metal |
Cabochon Polishing:
| Olson: | Chromium oxide on leather |
| Christiansen: | Aluminum, tin, or chromium oxide on leather or wood |
| Cox: | Aluminum or chromium oxide on leather, cerium oxide on felt |
| Covington: | Chromium or cerium oxide on felt |
Orientation:
For best yield
Treatments/Synthetics:
None
Tips!
Pyrope is often too brittle for coarse or new sanding discs.
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