Stilpnomelane is a phyllosilicate mineral of the mica

Mica

The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition...

 group. It has the formula

Chemical formula

A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 K(Fe²⁺,Mg,Fe³⁺)₈(Si,Al)₁₂(O,OH)₂₇.

Stilpnomelane occurs associated with banded iron formation

Banded iron formation

Banded iron formations are distinctive units of sedimentary rock that are almost always of Precambrian age. A typical BIF consists of repeated, thin layers of iron oxides, either magnetite or hematite , alternating with bands of iron-poor shale and chert...

s. It is a metamorphic mineral associated with the blueschist

Blueschist

Blueschist is a rock that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures, approximately corresponding to a depth of 15 to 30 kilometers and 200 to ~500 degrees Celsius....

 and greenschist

Greenschist

Greenschist is a general field petrologic term applied to metamorphic or altered mafic volcanic rock. The term greenstone is sometimes used to refer to greenschist but can refer to other rock types too. The green is due to abundant green chlorite, actinolite and epidote minerals that dominate the...

 facies

Metamorphic facies

The metamorphic facies are groups of mineral compositions in metamorphic rocks, that are typical for a certain field in pressure-temperature space...

.

It was first described in 1827 for an occurrence in Moravia

Moravia

Moravia is a historical region in Central Europe in the east of the Czech Republic, and one of the former Czech lands, together with Bohemia and Silesia. It takes its name from the Morava River which rises in the northwest of the region...

 in the Czech Republic

Czech Republic

The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....

. The name is derived from the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

stilpnos for shining, and melanos for black.