About
Most large Aragonite crystals are twinned growths of three individual crystals that form pseudohexagonal trillings. Although Aragonite crystallizes in the orthorhombic system, most prismatic crystals are hexagonally shaped due to the twinning. Trillings can be identified by their multi-directional basal striations from each individual member crystal.
Other minerals may form pseudomorphs after Aragonite. A peculiarity of the mineral world is Calcite after Aragonite, which is a pseudomorph after an existing paramorph. Some Aragonite crystals available to collectors are actually Calcite pseudomorphs after Aragonite. A rare but popular pseudomorph is Copper after Aragonite. Aragonite may also contain sand inclusions, which give a specimen a brown color.
A particularly interesting formation of Aragonite is as a deposition product of hot, mineral-rich springs. The water releases calcium upon emerging from the spring, and forms growing mounds and thick crusts around the springs. When these are banded, they may be carved and given trade names such as "Onyx Marble", and "California Onyx".
Aragonite is the main component of many organic substances, such as pearl and coral. The iridescent surface of Pearl and mother-of-pearl is actually a layer of Aragonite secreted by mollusks and related invertebrates. Some forms of Aragonite, especially the Flos Ferri variety, are brittle and very fragile, and may easily break when touched. Such specimens need to be much care.
Aragonite was named by Abrahan Gottlieb Werner after Molina de Aragón, Spain, the type locality where this mineral was first described.
Crystal Forms & Aggregates
Other ID Marks
2) Clear specimens display a visible double refraction.
Complex Tests
Striking Features
Environment
Varieties
✓ common · ✗ uncommon
- Flos Ferri— Filiform variety of Aragonite composed of wormlike intergrowths resembling branching coral.
- Mossottite— Strontium rich variety of Aragonite, or mixture of Aragonite and Strontianite. (Ca,Sr)CO3. Also known as Strontian Aragonite.
- Nicholsonite— Zinc rich variety of Aragonite. (Ca,Zn)CO3. Also known as Zincian Aragonite.
- Tarnowitzite— Lead rich variety of Aragonite, or mixture of Aragonite and Cerussite. (Ca,Pb)CO3. Also known as Plumboan Aragonite.
- Travertine— Mounds of calcium carbonate formed from hot springs that contain calcium-rich water that bubbles up to the earth and cools down, and its capability to hold calcium is reduced. The water eliminates the calcium, and the calcium forms a growing mound of calcium carbonate, which is porous. Travertine is usually Aragonite, although it may also be Calcite.
- Tufa— Aragonite (or Calcite) formed from precipitating water that traps in organic matter, such as leaves, twigs, and moss. Also calcareous mounds formed from deposition of hot springs that trap in organic matter.
- Alabaster— Massive, fine grained variety of Gypsum. Occasionally may also refer to a translucent, banded type of Aragonite in the form of Travertine or Tufa.
- Onyx Marble— Travertine or Tufa in the mineral form of Aragonite or Calcite that exhibits color banding.
- Satin Spar— Fibrous variety of Gypsum. May occasionally also describe a fibrous form of Calcite or Aragonite.
Polymorphs
Uses
Noteworthy Localities
Aragonite has come from Austria in a Siderite mine in Eisenerz, Styria (mainly in the Flos Ferri variety), and in the salt mines of Salzburg. The old iron mines at Frizington, Cumbria, England; as well as the locality of Vitosov, Moravia, Czech Republic; have both been good specimen producers.
A recent producer of specimen-grade Aragonite is Liupanshui, Guizhou Province, China. One of the most prolific occurrences for this mineral, in large trillings and in aggregates of reddish-brown crystals, is the Tazouta Mine near Sefrou, Morocco.
In the U.S., New Mexico has provided many fine Aragonite specimens at the Kelly Mine, Magdalena, Soccoro Co.; at Lake Arthur, near Roswell, Chaves Co; and at Las Cruces, Dona Ana Co. Fine Aragonite has also come from Bisbee, Cochise Co., Arizona; the Grand Deposit Mine, White Pine Co., Nevada; and the Northern Lights Mine, Hussman Spring, Mineral Co., Nevada. Other Western occurrences are Morro Bay, San Luis Obispo Co., California; the Oquirrh Mountains, Tooele Co., Utah; and Fort Collins, Larimer Co., Colorado. Midwestern and Eastern localities include Cave-in-Rock, Hardin Co., Illinois; Sterling Hill, Ogdensburg, Sussex Co., New Jersey; and Paterson and Prospect Park, Passaic Co., New Jersey.
Common Mineral Associations
Distinguishing Similar Minerals
Cerussite, Witherite, and Strontianite - Heavier.
Hemimorphite - Harder, heavier.
Photos
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