Common Forms/Occurrences: Found in ultramafic igneous rocks and marbles formed from metamorphosed limestone Useful Identification Test: Gelatinizes in HCl Chemical formula: (Fe,Mg)2SiO4 Crystal System: Short crystals that may resemble sand grains Colour: Pale or dark olive-green to yellow, or brown Streak: White Lustre: Nonmetallic (NM) Cleavage: Absent Fracture: Conchoidal Hardness: 7 Hardness Search: seven Specific Gravity: 3.3 - 3.4