Formula: Ca5(AsO4)3(OH)
Anhydrous arsenate containing hydroxyl, apatite group
Specific gravity: 3.68
Hardness: 4½
Streak: White
Colour: Light greyish white

Metamorphic environments

Johnbaumite occurs in skarn, commonly associated with biotite and calcite (Mindat).


At the Långban mine, Långban Ore District, Filipstad, Värmland County, Sweden, johnbaumite is associated with tilasite, andradite, calcite and caryopilite (HOM).

The type locality is the Franklin Mine, Franklin, Franklin Mining District, Sussex County, New Jersey, USA. Here johnbaumite occurs in metamorphic zinc-bearing skarn, associated with zincite, yeatmanite, roméite, franklinite, diopside, copper, calcite and andradite (Mindat, HOM). Johnbaumite is the massive matrix host for yeatmanite, which occurs in apparent chemical equilibrium with johnbaumite. Johnbaumite is also host to diopside, andradite, franklinite, copper and roméite. There are indications that diopside was the first phase to form; it is rimmed by andradite with inclusions of roméite in the andradite (AM 65.1143-1145).

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