Spessartine
One of the six end members in the garnet family. Spessartite is always orange, reddish-orange, or brownish-red.
Physical properties:
| Chemistry: | Mn+23Al2(SiO4)3 |
| Hardness: | 7.25 |
| SG: | 4.12-4.20 |
| Cleavage: | None |
| Fracture: | Sometimes slightly brittle |
| Heat sensitivity: | None |
Optical properties:
| RI: | 1.79-1.83 |
| Dispersion: | 0.027 (medium) |
| Double refraction: | None |
| Pleochroism: | None |
| Critical angle: | 34° |
Facet angles (pavilion/crown):
| Vargas: | 41°/39° |
| 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: | 40°/34° |
| Weikoff: | 42°/39° |
| Carroll: | 42°/35.1° |
Cutting lap:
Medium - fine
Facet polishing:
| Vargas: | Aluminum oxide on tin/lead, tin oxide on tin |
| Olson: | Chrome 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 typemetal |
Cabochon polishing:
| Olson: | Chrome oxide on leather |
| Christiansen: | Aluminum, tin, or chrome oxide on leather or wood |
| Cox: | Aluminum or chrome oxide on leather, cerium oxide on felt |
| Covington: | Chrome or cerium oxide on felt |
Orientation:
For best yield
Treatments/synthetics:
None
Tips!
Spessartite can be too brittle for coarse or new cutting laps. To distinguish between spessartite and hessonite, you can use a strong magnet. Spessartite is highly magnetic (stones under 4-5 ct can be lifted), while hessonite is largely unaffected.
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