225 - Pyrolusite

ID	225
Mineral	Pyrolusite
Location	Taylor mine - Alberta - Michigan - United States of America
Fluorescence	LW-UV: close SW-UV: close
Mindat.org	View Pyrolusite information at mindat.org

ID	3318
Long ID	1:1:3318:9
Formula	`MnO₂`
IMA Status	0 1
Other Occurrences	A common Mn mineral, although difficult to distinguish from similar Mn minerals, pyrolusite forms under oxidizing conditions and high pH. Mainly a mineral of lacustrine, shallow marine, and bog deposits, it is also found in the oxidized zones of manganiferous ore deposits and as deposits formed by circulating meteoric water. Both colloidal processes and bacterial action are important in its formation.
Diapheny	Opaque
Cleavage	Perfect on {110}.
Tenacity	brittle
Colour	Black or very dark grey.
Hardness (min)	2.0
Hardness (max)	6.5
About the name	Named in 1827 from the Greek for "fire" and "to wash," because it was used to remove brown and green tints in the making of glass.
Streak	Black to bluish-black.
Crystal System	Tetragonal
Cleavage Type	Perfect
Fracture type	Irregular/Uneven
Morphology	Crystals are uncommon, either long or short prismatic parallel to [001] or equant; more typically found as earthy powder or fibrous aggregates as crusts on rocks; sometimes as botryoidal aggregates, more rarely as druses of microscopic crystals. Never found as dendrites despite old literature. [The obsolete term "polianite" was once used to refer to crystalline pyrolusite, which was assumed to be a different species than earthy to crusty pyrolusite.]
Twinning	Twinning rare. Repeated twins with twin planes {031} and {032}. Polysynthetic twinning observed in polished sections.
UV	None.
shortcode_ima	Pyl
Group	Rutile Group

Symbol	Element
Mn	Manganese
O	Oxygen

Pyrolusite