Nontronite

Occurs in Pinal County.

Chemical Formula: Na_0.3(Al,Mg)₂(Si₄O₁₀)(OH)₂·nH₂O

Specific Gravity: 2.3-2.4

Luster: Pearly

Hardness: 1-2

Nontronite is a member of the smectite group of clay minerals. It often appears as greenish, scaly masses and is found in low-temperature hydrothermal environments.

Next Pinal County mineral: Nukundamite