Collinsite

A variety of Minerals

Collinsite specimen - rock identification

What is Collinsite?

Collinsite is translucent and brown, chocolate-black, light brown, yellowish white, white, or colorless. It is colorless in thin section and light yellow-brown to colorless in transmitted light. The zincian variety of collinsite is pale blue. The mineral can occur with fibrous habit, as globular aggregates of crystals, as concentrically layered botryoidal masses, or as bladed or prismatic crystals up to 2 cm (0.79 in). Collinsite is a member of the fairfieldite group. Hillite is the zinc analogue of collinsite and collinsite is the magnesium analogue of messelite.

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Collinsite Localities Map

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North ZoneCentral RidgeSouth Basin

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Key Characteristics

Formation of Collinsite

Collinsite has been found in Australia, Austria, Bahamas, Brazil, Canada, Germany, Namibia, Norway, Romania, Russia, South Africa, Spain, and the United States. The mineral formed as an incrustation of other minerals by weathering. It occurs in association with bitumen, bobierrite, carbonate rich fluoroapatite, cryptomelane, dolomite, Fe–Mn oxides, kovdorskite, parahopeite, and scholzite.

Composition of Collinsite

The crystal structure of collinsite was determined using essentially pure magnesian collinsite, Ca2Mg(PO4)2·2H2O, and published in 1974. It consists of chains of corner-sharing (MgΦ6) octahedra and (PO4) tetrahedra. Four of the Mg ligands link to (PO4) groups and the other two to water molecules. Two of the ligands in the (PO4) group link to (MgΦ6) octahedra and the other two link to calcium atoms and act as hydrogen bond acceptors. Weak hydrogen bonds link chains together and force separation between them. The separation gives room for interstitial, eight-coordinated calcium between chains.

More Images

Collinsite specimen 2
© Robert M. Lavinsky

Quick Facts

Physical Properties

Color
Light brown; light yellow-brown to colourless in transmitted light.
Hardness (Mohs)
3 - 3.5
Density
3.04 g/cm³
Streak
White

Chemical Properties

Chemical Formula
Ca2Mg(PO4)2 · 2H2O
Elements
Ca, H, Mg, O, P
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