Stottite

Chemical formula: Fe<sup>2+</sup>Ge(OH)<sub>6</sub>

Stottite is a rare mineral from the hydro-germanate group, forming small, tabular or dipyramidal crystals with a vitreous luster.

## Characteristics Stottite is a rare iron hydro-germanate, belonging to the mineral group of the same name. It occurs as small, well-formed crystals, usually not exceeding a few millimeters. Most often, it forms tabular or pseudo-octahedral (pyramidal) crystals, which can occur singly or in small aggregates. It is a brittle mineral with a vitreous or slightly greasy luster. ## Physical Properties Stottite is characterized by a hardness of 4.5 on the Mohs scale. Its density ranges from 3.59 to 3.65 g/cm³. It is transparent to translucent. It does not exhibit fluorescence under ultraviolet light. ## Colors and Varieties This mineral occurs in various shades of brown – from light brown, through reddish-brown, to dark brown. Specimens with a greenish or olive-green color are also found. Its color can depend on impurities and the degree of iron oxidation. No commercial names or varieties are distinguished for it. ## History and Name Stottite was discovered in the Tsumeb mine in Namibia, which is its type locality. It was first described in 1959 by German mineralogists: Karl F. J. Hugo Strunz, Gerhard Söhnge, and Bruno H. Geier. The mineral was named in honor of Sir Charles Ernest Stott, General Manager of Tsumeb Corporation, in recognition of his contribution to the mineralogical research of this deposit. ## Applications Stottite has no industrial applications. Its significance is purely scientific and as a collector's item, as a rare and well-formed representative of the germanate group.

Properties

Mohs hardness
4.5
Luster
Vitreous
Streak
Light brown
Density
3.59 - 3.65
Cleavage
Good on {001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Tetragonal

Diagnostic features

## Identification Stottite can be recognized by its characteristic crystalline form – small, pyramidal or tabular crystals. Its brown or greenish color, vitreous luster, and relatively low hardness are also important diagnostic features. Its occurrence in the oxidation zone of sulfide deposits rich in germanium is a key indicator. ## Distinguishing from Similar Minerals Stottite can be confused with other rare secondary minerals from the Tsumeb deposit. It is distinguished from the similarly looking brunogeierite by its color (brunogeierite is gray to black) and chemical composition. Identification often requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Crystal Forms Stottite crystals are typically small, with a pseudo-octahedral (dipyramidal) or tabular habit. They often exhibit a combination of different forms, giving them a complex appearance. They occur as single, overgrown crystals or in small groups on a rock matrix.

Geological environment

## Genesis Stottite is a secondary mineral, forming in the oxidation zones of hydrothermal, polymetallic sulfide deposits that are enriched in germanium. It forms as a result of the weathering and alteration of primary germanium-bearing minerals, such as germanite or reniérite. ## Mineral Associations This mineral co-occurs with other minerals of the oxidation zone, especially those rich in germanium. In the Tsumeb mine, it was found in association with tennantite, germanite, reniérite, galena, sphalerite, pyrite, chalcocite, as well as rarer secondary minerals such as anglesite, cerussite, smithsonite, otjisumeite, leiteite, and schneiderhöhnite. ## Localities The most important and classic locality for stottite is the Tsumeb mine in the Oshikoto region of Namibia, from which the world's best specimens originate. This is its type locality. Outside Namibia, its presence has been noted in very small quantities in the Kipushi mine in the Democratic Republic of Congo.

Rarity

Very rare

For collectors

## Quality Criteria The most prized stottite specimens are those with sharply defined, well-formed crystals with a distinct luster and intense, reddish-brown color. Specimens where a single, dominant crystal is aesthetically set on a contrasting matrix are highly valued. Crystal size is a key factor – specimens exceeding 5 mm are considered exceptional. Purity, meaning the absence of damage and inclusions, also significantly increases value. ## Popular Localities The only source of commercially significant collector's specimens of stottite is the historic Tsumeb mine in Namibia. Specimens from this locality are considered classics and serve as a benchmark for this mineral.

Care and storage

## Cleaning Stottite specimens should be cleaned very carefully, using a soft brush to remove dust. Distilled water may be used, but prolonged soaking should be avoided. After wet cleaning, the specimen should be dried immediately and thoroughly. ## What to Avoid Contact with acids and other aggressive chemicals, which can damage the mineral, should be avoided. Stottite is sensitive to temperature changes and should not be heated. As a secondary mineral, it can be unstable in conditions of low humidity or in contact with oxidizing substances. ## Storage It is recommended to store stottite under stable conditions, in closed containers or display cases, to protect it from dust, mechanical damage, and sudden changes in humidity. Due to its brittleness, it should be avoided to place it in direct contact with harder minerals.

Sources

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