’—“”₃₂₄₃—••—•²⁺••“”—’–’
This week's Member Box spotlight: Almandine Garnet -- the deep-red garnet most people picture when they hear "garnet.Fe3Al2(SiO4)3, a magnesium-free iron end-member of the pyralspite garnet series.This raw cluster comes from a schist host rock in Fujian Province, China. The crystals form classic rhombic dodecahedra (12- Chemical formula faced), sometimes modified by trapezohedra (24 faces) -- the most recognizable geometry in the mineral kingdom.
Member Box notes:
Formed under high pressure and temperature in metamorphic rock
- Mohs hardness 7.5 -- tough enough for industrial abrasive (sandpaper garnet!)
- Red color comes from ferrous iron substituting into the octahedral sites
- Distinguishes between almandine vs pyrope vs spessartine by exact iron/aluminum balance
- A classic starter stone for crystal system studies -- isometric, perfect symmetry
Fun geology fact: garnet-bearing schist is a pressure-temperature indicator. If you find crystals like these in the field, you know you're standing on rocks that were once buried 10 to 30 km deep. That's how old, dense collisional mountain belts become accessible at the surface.
