Schaurteite
Chemical formula: Ca<sub>3</sub>Ge(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>(OH)<sub>6</sub>·3H<sub>2</sub>O
A rare hydrated germanium and calcium sulfate, forming acicular, colorless crystals with a silky luster.
Properties
- Mohs hardness
- 2.5
- Luster
- Silky
- Streak
- White
- Density
- 2.62
- Cleavage
- Perfect on {0001}
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Hexagonal
Diagnostic features
## Identification Schaurteite can be identified by its characteristic form – it creates thin, acicular crystals gathered in radial or chaotic aggregates. Silky luster, white color of clusters, and extreme brittleness are also important indicative features. Its occurrence in the oxidation zone of sulfide deposits, especially in association with other germanium minerals, is a key clue. ## Distinguishing from Similar Minerals It can be confused with other acicular sulfates or carbonates, such as aragonite or natrolite. Differentiation often requires advanced analytical methods, such as Raman spectroscopy or chemical analysis (EDS/WDS) to confirm the presence of germanium. In the context of the Tsumeb locality, its association with other germanates is diagnostic. ## Crystal Forms Crystals are elongated and acicular, terminated by simple faces. They usually occur as radial aggregates resembling sea urchins or tangled clusters similar to glass wool.
Geological environment
## Genesis Schaurteite is a secondary mineral, forming in the oxidation zones of hydrothermal, polymetallic sulfide deposits rich in germanium. It forms as a result of the weathering of primary sulfides, such as germanite and renierite, under low temperature and pressure conditions. ## Mineral Associations It most often co-occurs with other rare minerals from the Tsumeb deposit, such as anglesite, tenorite, ludlockite, galena, germanite, renierite, as well as other secondary germanium sulfates and arsenates. ## Localities The only confirmed and classic locality of schaurteite in the world is the Tsumeb mine in the Oshikoto region of Namibia. This is its type locality, from which all known specimens of this mineral originate.
Rarity
Very rare
For collectors
## Quality Criteria The most prized schaurteite specimens are those that display well-formed, radial aggregates of acicular crystals, contrastingly set on a small rock matrix. The size and completeness of the aggregate and the absence of damage to the delicate needles are important. Color contrast with associated minerals, e.g., dark tenorite, significantly enhances the visual appeal of the specimen. ## Popular Localities The Tsumeb mine in Namibia is the sole source of this mineral. Specimens from this historic, now closed mine, are highly sought after by collectors specializing in rare minerals or minerals from this specific locality.
Care and storage
## Cleaning Schaurteite specimens are extremely delicate and brittle. Mechanical cleaning, including the use of brushes, should be avoided. If absolutely necessary, the specimen can be carefully rinsed in distilled water and then left to dry completely at room temperature, without using heat sources. ## What to Avoid Contact with all chemicals, including acids and detergents, should be avoided. The mineral is sensitive to high temperatures, which can lead to dehydration and destruction. It should be protected from vibrations and impacts. ## Storage It is recommended to store specimens in sealed, padded "micromount" boxes to protect them from dust, mechanical damage, and changes in humidity. Do not expose it to direct sunlight.