Paravauxite is a mineral that belongs to the wavellite group of phosphate minerals. It was named in 1922. Due to its chemical relationship to vauxite, its name is a portmanteau of the Greek word for near (meaning para) and vauxite. It is composed of aluminum, phosphorus, oxygen, and hydrogen. It was approved by the IMA and described for the first time in 1959. It is now grandfathered, which means it will almost certainly continue to exist as a species.
Paravauxite is typically found in granitic pegmatites, which are coarse-grained igneous rocks that contain large crystals. It is not commonly used for any commercial purposes, but it is a popular mineral among collectors due to its rarity and unique crystal structure. It was first described in 1956 and was named after the French mineralogist Gustave Paravaux.
General information
- Category: Mineral
- Formula (repeating unit): Fe2+Al2(PO4)2(OH)2 · 8H2O
- Crystal system: Triclinic
- Crystal class: Pinacoidal
- Unit cell: 334.43
- Color: Light brown, pale greenish white, gray-white, colorless
Properties
It is a member of the laueite supergroup, and the laueite group within said supergroup. It is metavauxite’s triclinic dimorph. It can form in complex granitic pegmatites, and in hydrothermal tin veins. The mineral is colorless in transmitted light. It mainly consists of oxygen (60.26%), but contains phosphorus (12.96%), iron (11.69%), aluminum (11.29%) and hydrogen (3.80%) as well. It doesn’t show any radioactive properties whatsoever.
- Formula mass: 477.89
- Cleavage: Perfect on {010}
- Fracture: Conchoidal
- Tenacity: Brittle
- Mohs scale hardness: 3
- Luster: Sub-Vitreous, resinous, waxy, pearly
- Streak: White
- Diaphaneity: Transparent, translucent
- Specific gravity: 2.36
- Density Measured: 2.36 (Calculated: 2.37)
- Optical properties: Biaxial (+)
Formation and mining
Other than vauxite and metavauxite, it is also associated with wavellite, but rarely occurs on the latter. It is the type locality of Llallagua, Bolivia. It can also be found in Germany, Mexico, the United States, Portugal, Sweden, with a couple of other countries.
Paravauxite is a relatively rare mineral, and it typically occurs as small, translucent to transparent crystals. It has a hardness of 3.5-4 on the Mohs scale, which means that it is relatively soft and can be scratched with a knife or a fingernail. Paravauxite is also known for its distinctive blue-green color, which is caused by the presence of copper ions in the crystal structure.
