Berlinite
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Berlinite is a rare high-temperature hydrothermal or metasomatic phosphate mineral. It has the same crystal structure as quartz with a low temperature polytype isostructural with α–quartz and a high temperature polytype isostructural with... Wikipedia
Crystal class: Trapezohedral (32); H-M symbol: (32)
Crystal habit: Typically granular to massive
Crystal system: Trigonal
Formula (repeating unit): AlPO4
Mohs scale hardness: 6.5
Optical properties: Uniaxial (+)
Space group: P3121, P3221