|
|
www.mineralgallery.co.za Minerals A-E |
|
|
Aragonite |
||
Name
Aragonite
Chemistry
CaCo3, Calcium Carbonate
Uses
Used in cement as lime and also used as a mineral specimen
Color
Usually white or colorless or with soft shades of red yellow, brown or green
Hardness
3.5-4
Specific gravity
2.9-3.1
Crystals
The crystal system is orthorhombic. The crystals are not twinned like calcite, they are single. Crystals are rare and may be acicular or tabular. They might have a pseudo-hexagonal symmetry. It also occurs as stactitic and encrusting masses
Accompanied by:
Jadeite and glaucophane
Fracture
Subconchoidal
Luster
Vitreous
Cleavage
Pinacoidal, imperfect
Streak
White
Similar to:
Calcite
Aragonite is a carbonate mineral.
It has interesting habits. It has exactly the same chemical make-up as calcite. It is thus a polymorph of calcite. The most interesting crystals, cyclic twins, occur in Spain and Morocco. Corals and some sea creatures secrete aragonite for their shells. It is also found around hot springs and in caves.
The ones we have available comes from the Sterkfontein cave complex. These caves are reputed to stretch for over a hundred kilometer underground. Some of the holes had to be filled and the geologist who was responsible for the blasting got these specimens for me. No caves were raided to obtain them.
Aragonite is the less common and stable of the two, calcium carbonate minerals; the other is calcite. Occurring in near-surface deposits, aragonite forms crystals that are glassy-white, slender, and tapering, as well as columnar masses, stalactites, and crusts. Some specimens fluoresce green (see fluorescence).
Aragonite is formed through organic agencies as pearl and mother-of-pearl; it is precipitated as a hot-spring deposit and in beds with gypsum as an evaporate deposit.
The name comes from the province in Spain, Aragon where it was first noted.
Aragonite at Tsumeb
Relatively pure aragonite forms slightly greenish to bluish needles and turquoise-colored radially structured masses and crusts; it occurs very rarely in dull, prismatic, pseudohexagonal crystals. It is far more scarce than calcite.
