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Occurs in Pinal County.

Chemical Formula: Mg3(Si2O5)(OH)4

Specific Gravity: 2.5-2.6

Luster: Pearly

Hardness: 3.5-4

Antigorite is a serpentine mineral and is one of the polymorphs of serpentine. It typically forms as green to dark green masses and is associated with serpentinite rocks.

Next Pinal County mineral: Antimony

MinDat Antigorite

Antigorite is a mineral belonging to the serpentine group, which is a group of minerals that are typically green, hydrous (water-containing) magnesium silicates. Antigorite is one of the main mineral forms of serpentine and is known for its fibrous and often silky appearance.

Key characteristics of antigorite include:

  1. Crystal Structure: Antigorite belongs to the monoclinic crystal system. Its crystal structure is characterized by sheets of silicon-oxygen tetrahedra that are bonded to sheets of octahedral magnesium hydroxide layers.
  2. Color and Luster: Antigorite is typically green in color, ranging from pale to dark green. It can have a vitreous (glassy) or silky luster, which is often due to its fibrous and mineralogical structure.
  3. Fibrous Habit: Antigorite commonly forms in fibrous aggregates, meaning that its crystals grow together in long, slender fibers. These fibers are often interwoven and give the mineral a silky appearance.
  4. Occurrence: Antigorite is a common mineral in serpentinite rock, which forms through the metamorphism of ultramafic rocks (rocks rich in magnesium and iron). It is often associated with hydrothermal alteration of rocks deep within the Earth’s crust.
  5. Asbestos: Certain forms of antigorite have been associated with asbestos minerals, which are known for their fibrous and heat-resistant properties. Asbestos minerals, including certain types of antigorite, can be hazardous to human health when inhaled as fine dust particles.
  6. Uses: Antigorite itself is not widely used in industrial or commercial applications. However, other minerals in the serpentine group, particularly chrysotile (a type of asbestos), were historically used in various products such as building materials and insulation, though their use is now restricted due to health concerns.