THE MINERAL PURPURITE

Chemistry: MnPO4, Manganese Phosphate
Class: Phosphates
Uses: Only as a mineral specimens.
Specimens

Purpurite forms a series with the mineral heterosite. Purpurite is the manganese rich end member and heterosite is the iron rich end member. Purpurite is a very rare mineral that would get much attention in the semi-precious stone market due to its striking color, if it were not for this rarity. Purpurite is an alteration product of an equally rare mineral called lithiophyllite, LiMnPO4. The alteration takes place atom by atom and actually forms what is called a pseudomorph or "false shape". A pseudomorph is a mineral that has the shape of one mineral but has a different chemistry and/or structure.

The alteration is an oxidation reaction with the manganese ion going from a positive two (+2) charge in lithiophyllite to an ion with a positive three (+3) charge in purpurite. With the change in charge in the manganese ion, the lithium ion is then lost. Often some of the original lithiophyllite is still present in most purpurite specimens. The purple color or purpurite is truly unique in the mineral rainbow.

PHYSICAL CHARACTERISTICS:

Color is purple (hence the name).
Luster is vitreous to sub-metallic.
Transparency: Crystals are translucent to opaque.
Crystal System is orthorhombic; 2/m2/m2/m
Crystal Habits generally are massive grains or crusts.
Cleavage is good in one and poor in another direction.
Fracture is uneven.
Hardness is 4 - 4.5.
Specific Gravity is approximately 3.3 (above average)
Streak is deep red to purple.
Other Characteristics: Brown coatings can be removed by weak acid baths that can also bring out more purple color.
Associated Minerals are lithiophyllite, heterosite, quartz and feldspars.
Notable Occurrences include Namibia; western Australia; North Carolina, USA and France.
Best Field Indicators are color, associations, lack of crystals and luster.