ARAGONITE - Aragonite is a polymorph of calcite, which means that it has the same chemistry as calcite but it has a different structure, and more importantly, different symmetry and crystal shapes.
CHEMISTRY: CaCO3 (Calcium carbonate, sometimes with some strontium, lead, and zinc)
HARDNESS: 3.5 - 4
CRYSTALLOGRAPHY: Orthorhombic; 2/m 2/m 2/m
Crystal Habits include twinned hexagonal prismatic crystals as well as a diverse assortment of thin elongated prismatic, curved bladed, steep pyramidal (spiked) and chisel shaped crystals. A branching tree, coral or worm-like delicate form is called "flos ferri". Can also be compact, granular, radially fibrous and massive. Its massive forms can be layered, coralloid, pisolitic, oolitic, globular, stalachtitic and encrusting. Aragonite is a constituent of many species' shell structures. A layered sedimentary marble like formation is called Mexican Onyx and is used for carvings and ornamental purposes. Calcite pseudomorphs of aragonite crystals and formations are common.
SPECIFIC GRAVITY: 2.9+ (average for non-metallic minerals)
REFRACTIVE INDEX: 1.7
COLOR: white or colorless or with usually subdued shades of red, yellow, orange, brown, green and even blue.
Luster is vitreous to dull. Crystals are transparent to translucent.
Cleavage: 3,1 - prismatic ; indiscernible,2 (distinct in one direction (pinacoidal)
Fracture is subconchoidal.
Streak is white.
Other Characteristics: aragonite effervesces easily in cold dilute hydrochloric acid, is strongly birefringent, and is fluorescent.
Associated Minerals include gypsum, barite, smithsonite, malachite, calcite, serpentine, sulfur, celestite, zeolites, quartz, clays, dolomite, limonite, chalcopyrite and wulfenite among many others.
Notable Occurrences include Aragon, Spain (its type locality and from where it gets its name); Morocco; Bastennes, France; Girgenti, Sicily; Alston Moor and Cleator Moor, Cumberland, England; Baja California, Mexico (Mexican Onyx); Tsumeb, Namibia; Carinthia, Austria; Leadhills, Scotland; Harz Mountains, Germany and in several localities in the Southwestern United States.
Best Field Indicators are crystal habits, single plane of cleavage and reaction to acid.
Aragonite is a common carbonate mineral. It is unfortunately often thought of as the poor cousin to calcite. But aragonite is an interesting and attractive mineral in its own right. It forms interesting habits and can have a soft pretty color. Its modes of formation and relationship to calcite are both curious and intriguing.
Aragonite also has another popular habit called flos ferri or "flowers of iron". This is a branching, clumpy habit that can make delicate tree, coral or worm-like formations that are most unique. A steep pyramidal habit forms clusters of sharp spiked crystals sometimes referred to as a "church steeple" habit. Aragonite is a constituent of many sea creatures' shell structures; a curious development since calcite is the more stable form of calcium carbonate. Most bivalve animals and corals secrete aragonite for their shells and pearls are composed of mostly aragonite. The pearlization and iridescent colors in sea shells such as abalone are made possible by several minute layers of aragonite. Other environments of formation include hot springs deposits, cavities in volcanic rocks, caves and mines.
Metaphysical Properties:
- Aids in grounding and centering.
- Aragonite is also useful in overcoming illusions, and help one to face truth and accept reality.
