Brushite – Occurrence, Properties, and Distribution

Brushite was named after Professor George Jarvis Brush (1831–1912), an American mineralogist associated with Yale University in New Haven, Connecticut, USA.

Properties of Brushite

The following are the key properties of brushite:

• Cell Data
  • Space group: C2/c
  • a = 6.361(3)
  • b = 15.191(4)
  • c = 5.814(2)
  • β = 118.45(4)°
  • Z = 4

• Crystal Data
  • Monoclinic
  • Point group: 2/m
  • Crystals are needle-like, prismatic to tabular {010}, to 2cm
  • May be foliated
  • Usually powdery or earthy
  • X-ray powder pattern: 7.62 (100), 3.80 (31), 1.90 (10), 3.06 (8), 2.53 (6), 4.27 (2), 2.63 (1)

• Chemical Composition

  Elements	Content 1	Content 2
  P2O5	41.41	41.24
  CaO	32.69	32.59
  H2O	26.36	26.17
  Total	100.46	100.00

• Optical Properties
  • Optical class: Biaxial (+)
  • Orientation: Z = b; X ^ c = –30°
  • Dispersion: r > v, noticeably crossed
  • α = 1.539–1.540; β = 1.546; γ = 1.551–1.552
  • 2V(meas.) =59°- 90°

• Estimated Properties

  Electron density	Bulk density (electron density) = 2.38 g/cm3 note: Specific gravity of brushite = 2.33 g/cm3
  Photoelectric	PEBrushite = 3.72 barns/electron U=PEBrushite x ρ electron density= 8.85 barns/cm3
  Fermion index	Fermion index = 0.0005865581 Boson index = 0.9994134419
  Radioactivity	Brushite is not radioactive

How to Identify Brushite

Brushite can be identified in the field by its color variations, such as yellow, yellowish white, and white. It is sometimes colorless. Its transparent to translucent form has {010} perfect and {001} perfect cleavage.

This mineral has a vitreous - pearly luster with white streak. The density of brushite is 2.328 g/cm³, with a hardness of 2.5 – approximate to a finger nail.

Global Distribution

Brushite is distributed in the following places:

• Venezuela - Found on Aves Island, west of Dominica in the Caribbean Sea
• West Indies - From Sombrero Island
• Puerto Rico - On Mona Island
• USA - In Pig Hole Cave, Giles Co. Virginia; along Rock Creek, Kankakee Co. Illinois; in Kartchner Cavern, near Benson, Cochise Co. Arizona
• France - Large crystals from Quercy, near Limoges, Haute-Vienne
• Germany - At Schneeberg, Saxony
• England - From Wheal Cock, St. Just, Cornwall
• Algeria - At Oran
• Namibia - From the Tsaobismund pegmatite, 60km south of Karibib
• Japan - In Kyusen-do Cave, Kumamoto Prefecture
• Australia - From the Skipton lava tube caves, 40km southwest of Ballarat, Victoria
• Antarctica - In the Vestfold Hills, East Antarctica

Occurrence of Brushite and Useful Mineral Association

Brushite is one of the most common cave minerals. It occurs in guano deposits, and in phosphorites that are formed at low pH by reaction of phosphate-rich solutions with calcite and clay.

It is often associated with minerals such as tanarakite, variscite, ardealite, hydroxylapatite, and gypsum.

References

• Brushite - RruffProject Website-University of Arizona
• Brushite - Webmineral
• Brushite - Mindat