GOYAZITE
Class : Phosphates, arsenates, vanadates
Subclass : Hydrated phosphates
Crystal system : Trigonal
Chemistry : SrAl3(PO4)2(OH)5 H2O
Rarity : Uncommon
Goyazite (also called hamlinite) is an uncommon phosphate from magmatic and hydrothermal contexts; it is indeed found in granitic pegmatites and greisens, zones of clayey hydrothermal alteration, carbonatites, etc... Resistant, it is also an alluvium mineral. It owes its name to its locality of discovery : Serra de Congonhas in the province of Goyaz (Brazil). Goyazite crystals are rhombohedral, sometimes pseudocubic or tabular, colorless or whitish, straw yellow to yellow-brown, sometimes orange.
Main photo : Goyazite from Binn, Valais, Switzerland © Stephan Wolfsried
Goyazite in the World
Twinning
No twin known for this mineral species.
Fakes and treatments
No fakes recorded for this mineral species.
Hardness : 4.5 to 5
Density : 3.26
Fracture : Undetermined
Streak : White
TP : Translucent to transparent
RI : 1.620 to 1.651
Birefringence : 0.013
Optical character : Uniaxial +
Pleochroism : Low
Fluorescence : None
Solubility : Acids
Magnetism : NoneRadioactivity : None