Groutite

Occurs in Pinal County.

Chemical Formula: Mn₃+O(OH)

Specific Gravity: 4.4-4.6

Luster: Metallic to submetallic

Hardness: 5-5.5

Groutite is a manganese oxide mineral that often appears as black to dark brown crystals or crusts. It is found in manganese deposits.

Next Pinal County mineral: Gypsum