Paravauxite , Sigloite Locality: Siglo Veinte Mine (Siglo XX Mine; Llallagua Mine; Catavi), Llallagua , Rafael Bustillo Province , Potosí Department , Bolivia ( Locality at mindat.org ) Size: 7.8 x 4.5 x 3.8 cm. These crystals are one of the most beautiful phosphates in the world. They are highly prized for their rarity and beauty. This piece features superb, incredibly rare, sharp, semi lustrous, light green crystals of Paravauxite with tan colored crystal of Sigloite on matrix. Sigloite forms as the result of alteration from Paravauxite. This specimen is from the type locality for both species! Mark Chance Bandy described Paravauxite crystals in his book "Mineralogy of Llallagua, Bolivia". He states that Paravauxite is the most abundant of all the "Vauxites" from this mine," and with that said, you almost never see specimens, especially pieces that are larger than thumbnails available on the market. This piece is a great example of the prismatic, sheaf-like parallel growths that Mr. Bandy described. Ex. Brian Kosnar. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Sigloite
Sigloite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Fe³⁺Al₂(PO₄)₂(OH)₃·7H₂O.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Laueite structural group.
Key properties: Mohs hardness 3; specific gravity 2.35; optically biaxial.
IMA symbol Sig, IMA status: approved, named in 1962.
A rare late-stage secondary mineral, produced through oxidation of vauxite, in open fractures cutting cassiterite veins in a hydrothermal tin deposit.
It is found associated with Wavellite, metavauxite, crandallite, childrenite, vauxite, quartz.
The name refers to its occurrence in the Siglo XX mine, Llallagua, Bolivia.