PHYSICAL CHARACTERISTICS:
Color can be white or colorless or with usually subdued shades of red, yellow, orange, brown, green and even blue.
Luster is vitreous to dull.
Transparency: Crystals are transparent to translucent.
Crystal System is 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.
Cleavage is distinct in one direction (pinacoidal).
Hardness is 3.5-4
Streak is white.
Other Characteristics: aragonite effervesces easily in cold dilute hydrochloric acid, is strongly birefringent, is fluorescent and
its refractive index is 1.7.
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.