Keplerite

keplerite

merrillite

stanfieldite

maghemite

Images

Formula: Ca9(Ca0.50.5)Mg(PO4)7
Phosphate, merrillite subgroup, merrillite group, cerite supergroup
Crystal System: Trigonal
Specific gravity: 3.122 calculated
Streak: White
Colour: Colourless
Luminescence: Not fluorescent under UV
Environments

Metamorphic environments
Meteorites

Keplerite is a new mineral, approved in 2020, that occurs in some pallasite and angrite meteorites. It is an indicator of high-temperature environments characterised by extreme depletion of Na (HOM).

Localities

At the Aravaite type locality, Hatrurim Basin, Tamar Regional Council, Southern District, Israel, keplerite occurs in brecciated, altered pyroxene paralava (fused sediments) by pyrometamorphism. Associated minerals include fluorapatite, maghemite and stanfieldite (HOM).
The association of keplerite with “REE - merrillite” and stanfieldite provides evidence for the similarity of temperature conditions that occurred in the Mottled Zone (Hatrurim Formation) to those expected during the formation of pallasite meteorites and lunar rocks (AM 106.1917-1927)

At the type locality, the Marjalahti meteorite, Viipuri, Ladoga Region, Republic of Karelia, Russia, keplerite occurs in the main-group pallasites and angrites. It is the Ca-dominant counterpart of the most abundant meteoritic phosphate, which is merrillite. The Marjalahti meteorite is the main group pallasite.
Keplerite grains in Marjalahti have an ovoidal to cloudy shape and reach 50 μm in size. The mineral is colourless and transparent with a vitreous lustre. Cleavage was not observed. In transmitted light, keplerite is colourless and non-pleochroic. It is an indicator of high temperature environments characterised by extreme depletion of Na. The association of keplerite with “REE - merrillite” and stanfieldite provides evidence for the similarity of temperature conditions that occurred in the Mottled Zone (Hatrurim Formation) to those expected during the formation of pallasite meteorites and lunar rocks (AM 106.1917-1927)

Back to Minerals