Brockite

Brockite
General
Category Phosphate mineral
Formula
(repeating unit)
(Ca,Th,Ce)PO4·H2O
Strunz classification 08.CJ.45
Crystal system Hexagonal
Unit cell a = 6.98 Å, c = 6.40 Å; Z=3
Identification
Color Reddish brown, yellow (red brown due to inclusions of hematite)
Crystal habit Rarely as Stubby hexagonal prisms rare; common as granular massive aggregates, cryptocrystalline
Crystal symmetry Hexagonal trapezohedral
H-M symbol: (6 2 2)
Space group: P 6222
Cleavage None observed
Fracture Conchoidal
Tenacity Brittle
Mohs scale hardness 3 - 4
Luster Greasy to vitreous
Diaphaneity Translucent to opaque
Specific gravity 3.9 (measured)
Optical properties Uniaxial (+)
Refractive index nω = 1.680 nε = 1.695
Birefringence δ = 0.015
Other characteristics Radioactive
References [1][2][3]

Brockite is a rare earth phosphate mineral with formula: (Ca,Th,Ce)PO4·H2O. It crystallizes in the hexagonal system. It is typically granular to massive with only rare occurrence of stubby crystals. It is radioactive due to the thorium content.

Discovery and occurrence

Brockite was first described in 1962 for an occurrence in the Bassick Mine area, Querida, Wet Mountains, Custer County, Colorado, US. It was named for Maurice R. Brock, of the U.S. Geological Survey.[2]

Brockite occurs in granite and granite pegmatite as an accessory mineral. Associated minerals include monazite, bastnasite, xenotime, thorite, zircon, apatite, rutile and hematite.[1]

References

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