- Chemistry: FeAl2(PO4)2(OH)2
- 8H2O, Hydrated Iron Aluminum Phosphate Hydroxide.
- Class: Phosphates
- Group: Paravauxite.
- Uses: Only as mineral specimens.
Paravauxite is closely related to its basic namesake vauxite.
Paravauxite appears to be different from vauxite only in the number of
water molecules in the structure. Paravauxite has eight water molecules
while vauxite has only six in its formula. It is the presence of these
water molecules that alters the structure to the point that paravauxite
has perfect cleavage while in sharp contrast, vauxite has no cleavage at
all. Cleavage is one property that is undeniably tied to the structure
of a mineral. The only other strikingly different property is paravauxite's
green to colorless color verses vauxite's blue color.
is another closely named and closely related mineral to paravauxite. It
is a dimorph of paravauxite. A dimorph is a mineral that has the same chemistry,
but a different structure. In this case, the structure of paravauxite is
triclinic while the structure of metavauxite is monoclinic in symmetry.
Although one might think so, vauxite and paravauxite are not dimorphs
since they share neither the same structure (although both are triclinic)
nor the same chemistry (thanks to those water molecules). Vauxite, paravauxite
and metavauxite are all found at the famous tin oxide deposits at Llallagua,
Potosi, Bolivia. All are associated with the primary tin ore, cassiterite.
They form as a result of precipitation from hydrothermal solutions.
Paravauxite is the name of a somewhat rare
phosphate mineral and an obscure mineral group. The Paravauxite Group
is composed of other triclinic phosphates that have the following general
The X ion can be either iron(+2),
magnesium, manganese or iron(+3) while the Y
ion can be either aluminum, iron(+3) or to a lesser extent, chromium. The
second formula is used when the X ion
is the iron(+3) in stead of the iron(+2) and the additional positive charge
requires the additional hydroxide and one less water molecule.
These are the members of the Paravauxite Group with their respective
- Gordonite MgAl2(PO4)2(OH)2
- Laueite MnAl2(PO4)2(OH)2
- Paravauxite FeAl2(PO4)2(OH)2
- Sigloite FeAl2(PO4)2(OH)3
- Ushkovite MgFe2(PO4)2(OH)2
- Color is colorless, white or pale green.
- Luster is vitreous to pearly.
- Transparency: Specimens are translucent to transparent.
- Crystal System is triclinic.
- Crystal Habits include tabular crystals and radiating fibrous
- Cleavage is perfect.
- Fracture is conchoidal.
- Hardness is 3
- Specific Gravity is approximately 2.4 (average).
- Streak is white.
- Associated Minerals include
- Notable Occurrences are limited to the famous tin deposits at
Llallagua, Potosi, Bolivia and a few minor localities around the world.
- Best Field Indicators are color, locality, crystal habit, associations
and perfect cleavage.