Psilomelane is a group name for hard black manganese oxides including hollandite and romanechite. Psilomelane consists of hydrous manganese oxide with variable amounts of barium and potassium. Psilomelane is erroneously, and uncommonly, known as black hematite, despite not being related to true hematite, which is an iron oxide.
Manganese oxide in the context of Clay earth pigment
Earth pigments are naturally occurring minerals that have been used since prehistoric times as pigments. Among the primary types of earth pigments include the reddish-brown ochres, siennas, and umbers, which contain various amounts of iron oxides and manganese oxides. Other earth pigments include the green earth pigments or terres vertes, blue earth pigments such as vivianite-based "blue ochre", white earth pigments such as chalk, and black earth pigments such as charcoal.
Earth pigments are known for their fast drying time in oil painting, relative inexpensiveness, and lightfastness. Cave paintings done in sienna still survive today.
Umber is a natural earth pigment consisting of iron oxide and manganese oxide; it has a brownish color that can vary among shades of yellow, red, and green. Umber is considered one of the oldest pigments known to humans. Umber's advantages are its highly versatile color, warm tone, and quick drying abilities. While some sources indicate that umber's name comes from its geographic origin in Umbria, other scholars suggest that it derives from the Latin word umbra, which means "shadow". The belief that its name derives from the word for shadow is fitting, as the color helps create shadows. The color is primarily produced in Cyprus. Umber is typically mined from open pits or underground mines and ground into a fine powder that is washed to remove impurities. In the 20th century, the rise of synthetic dyes decreased the demand for natural pigments such as umber.
Manganese oxide in the context of Salt glaze pottery
Salt-glaze or salt glaze pottery is pottery, usually stoneware, with a ceramic glaze of glossy, translucent and slightly orange-peel-like texture which was formed by throwing common salt into the kiln during the higher temperature part of the firing process. Sodium from the salt reacts with silica in the clay body to form a glassy coating of sodium silicate. The glaze may be colourless or may be coloured various shades of brown (from iron oxide), blue (from cobalt oxide), or purple (from manganese oxide).
Except for its use by a few studio potters, the process is obsolete. Before its demise, in the face of environmental clean air restrictions, it was last used in the production of salt-glazed sewer-pipes. The only commercial pottery in the UK currently licensed to produce salt glaze pottery is Errington Reay at Bardon Mill in Northumberland which was founded in 1878.
Romanèchite ((Ba,H2O)2(Mn,Mn)5O10) is the primary constituent of psilomelane, which is a mixture of minerals. Most psilomelane is not pure romanechite, so it is incorrect to consider them synonyms. Romanèchite is a valuable ore of manganese, which is used in steelmaking and sodium battery production. It has a monocliniccrystal structure, a hardness of 6 and a specific gravity of 4.7–5. Romanèchite's structure consists of 2 × 3 tunnels formed by MnO6 octahedra.
Sienna (from Italianterra di Siena'earth of Siena') is an earth pigment containing iron oxide and manganese oxide. In its natural state, it is yellowish brown, and it is called raw sienna. When heated, it becomes a reddish brown, and it is called burnt sienna. It takes its name from the city-state of Siena, where it was produced during the Renaissance. Along with ochre and umber, it was one of the first pigments to be used by humans, and is found in many cave paintings. Since the Renaissance, it has been one of the brown pigments most widely used by artists.
The first recorded use of sienna as a color name in English was in 1760.
Cristallo is a glass that is totally clear (like rock crystal), without the slight yellow or greenish color originating from iron oxide impurities. This effect is achieved through small additions of manganese oxide. Cristallo often has a low lime content, which makes it prone to glass corrosion (otherwise known as glass disease).
The invention of Cristallo glass is attributed to Angelo Barovier around 1450.