Mineral - Aragonite
Aragonite
Chemical Properties
Mineral Class
Carbonates
Toxicity
none
Formula
CaCO₃
Unit Cell
a=4.96 b=7.97 c=5.74 Z=4
Physical Properties
Hardness
3.5 - 4
Streak
white
Density
Normal (2-3,5)
Cleavage
Distinct after {010}, very poor after {110} and {011}
Fracture
conchoidal
Tenacity
Brittle
Optical Properties
Color
whiteredyellowgreenbluepinkvioletcolorless
Birefringence
0.156
Luster
Vitreous
Transparency
translucent,
transparent,
opaque
Pleochroism
Geomineralogical Properties
Crystal System
orthorhombic
Point Group
orthorhombic-dipyramidal - 2/m 2/m 2/m
Space Group
Pnma (62)
Habit
dendritic, coarse, crusty, spherical, acicular, prismatic, Scalenohedron, spear-shaped, spear-shaped, Rhombohedral, stalactitic, prismatic, radial, tabular
Formation
Main component of many shells/skeletons of organisms
Sedimentary, as primary precipitate from seawater (e.g. oolites)
Secondary through the rearrangement in sediments
Secondary, through the weathering of igneous rocks
Kinetically unstable on the earth's surface (reacts to calcite)
Paragenesis
Twinning
Rotation twins after {110} form pseudohexagonal octagons
Rarity
Very common
Synonyms
Aragonite
Composition
Elements
Mass
CO₂
43.95
CaO
0.03
MgO
55.96
Japan (Palache et al. 1952)
Groups and Members
Aragonite-Group
Name and first record : Named after the type locality near the town of Molina de Aragón, Spain. First described in 1792.
Chemistry : Polymorph with calcite and vaterite
Synonyms : Arragonite, Chimborazite, Conchite, Iglite, Igloite, Ktypéite, Needlestone, Oserskite
Varieties : Eisenblüte, Flos-Ferri, Pelagosite, Sr-Aragonite, Tarnowitzite, Zeiringite, Zn-Aragonite
Abbreviation : Arg
literature
Palache, C., Berman, H., & Frondel, C. (1952). Dana's system of mineralogy. Geologiska Föreningen i Stockholm Förhandlingar , 74 (2), 218-219.