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Aragonite

Occurs in Pinal County. Common in Arizona.

Chemical Formula: CaCO3

Specific Gravity: 2.9-3.0

Luster: Vitreous to pearly

Hardness: 3.5-4

Aragonite is a carbonate mineral that is one of the polymorphs of calcium carbonate. It can be found in various forms, including stalactites, stalagmites, and in some shells and corals.

Next Pinal County mineral: Atacamite

MinDat Aragonite

Aragonite is a mineral that belongs to the carbonate mineral group. It is a polymorph of calcium carbonate, meaning it has the same chemical composition as calcite (CaCO3), but a different crystal structure. Aragonite is named after the Spanish town of Molina de Aragón, where it was first discovered.

Key characteristics of aragonite include:

  1. Crystal Structure: Aragonite crystallizes in the orthorhombic crystal system. Its crystal structure is more compact and elongated compared to the rhombohedral structure of calcite.
  2. Color and Transparency: Aragonite can exhibit various colors, including white, gray, brown, and even shades of blue and green. It can be transparent to translucent.
  3. Habit: Aragonite crystals can form in various habits, including prismatic, acicular (needle-like), and twinned structures. These crystal habits contribute to its unique appearance.
  4. Occurrence: Aragonite is found in a variety of geological environments. It can form in sedimentary, metamorphic, and igneous rocks. It is commonly found in sedimentary deposits such as limestone caves and hot springs, as well as in seashells and coral skeletons.
  5. Biogenic Aragonite: Many marine organisms, such as corals, mollusks, and certain types of algae, use aragonite to build their shells and skeletons. These biogenic deposits contribute to the formation of limestone and other sedimentary rocks.
  6. Use and Applications: Aragonite is valued as a decorative and ornamental stone. It is often cut and polished into cabochons, beads, and other jewelry items. It is also used as a source of calcium carbonate in various industrial applications, including agriculture, construction, and as a supplement in animal feed.
  7. Pseudomorphs: Aragonite can sometimes undergo pseudomorphism, where its crystal structure is replaced by another mineral while retaining the original shape. For example, aragonite pseudomorphs after gypsum are relatively common in certain geological settings.