Rudolfhermannite

Chemical formula: Fe³⁺₂(Te⁴⁺O₃)₃·H₂O

Rudolfhermannite is an extremely rare iron tellurite, forming microscopic, orange-red crystals with a strong, adamantine luster.

## Characteristics Rudolfhermannite is a mineral from the oxide group, specifically an iron tellurite. It occurs as very small, tabular or bladed crystals, rarely exceeding 0.2 mm in length. These crystals often form radial or chaotic aggregates. Its most characteristic features are its intense, orange-red to reddish-brown color and an exceptionally strong, almost adamantine luster, which distinguishes it from other minerals. ## Physical Properties This mineral is very soft, with a Mohs hardness of only 2. It is transparent to translucent. Due to the microscopic size of its crystals, many of its physical properties, such as density or fracture, have not been precisely determined. ## Colors and Varieties Rudolfhermannite occurs in uniform, vivid colors ranging from orange-red to reddish-brown. No color varieties or commercial varieties are known. ## History and Name The mineral was discovered in the dumps of the Bambolla mine (Bambollita) near Moctezuma, Sonora, Mexico. It was described and approved as a new mineral species by the International Mineralogical Association (IMA) in 2017. The name "rudolfhermannite" honors Rudolf Hermann (1805-1879), a German chemist and mineralogist who first described tellurium as an element in a mineral from Mexico. ## Uses Due to its extreme rarity and microscopic size, rudolfhermannite has no industrial applications. It is solely of scientific importance and is a coveted object for specialized micromineral collectors.

Properties

Mohs hardness
2
Luster
Adamantine
Streak
Light orange
Cleavage
Perfect on {010}
Transparency
Transparent to Translucent
Crystal system
Hexagonal

Diagnostic features

## Identification Rudolfhermannite can be identified by its characteristic, intense orange-red color, very strong, adamantine luster, and typical form of small, tabular crystals forming radial aggregates. Its location is also key – it occurs in paragenesis with other rare tellurites. ## Distinguishing from Similar Minerals It can be confused with other rare, colorful tellurites from Moctezuma, such as emmonsite, mackayite, or poughite. Definitive differentiation requires advanced analytical methods, such as Raman spectroscopy or chemical analysis (EDS), due to visual similarity and co-occurrence. ## Crystal Forms It forms very small, thin, tabular crystals with a hexagonal or rectangular outline, often elongated in one direction, resembling blades. These crystals combine into radial, stellate, or chaotic aggregates on the surface of the host rock.

Geological environment

## Genesis Rudolfhermannite is a secondary mineral, forming in the oxidation (weathering) zone of ore deposits containing tellurium. It forms under low temperature and pressure conditions as a result of the alteration of primary tellurides. Its type locality is hydrothermal quartz veins rich in tellurium. ## Mineral Associations It most commonly co-occurs with quartz, barite, emmonsite, tellurite, as well as other, even rarer tellurites and tellurates of iron, zinc, and copper, characteristic of the Moctezuma deposit. ## Localities The only confirmed locality of rudolfhermannite in the world is its type locality: the Bambolla mine (Bambollita) in the municipality of Moctezuma, Sonora State, Mexico.

Rarity

Extremely rare

For collectors

## Quality Criteria The most highly valued specimens are those with rich, dense clusters of well-formed, radial aggregates of intense, orange-red color. Contrast with the light host rock (most often quartz) and the absence of damage to the delicate crystals are also important. The size of individual crystals, even if they are fractions of a millimeter, significantly increases the value of the specimen. ## Popular Localities The only source of specimens of this mineral is the historical dumps of the Bambolla mine in Moctezuma, Mexico. The material comes from old dumps, and the acquisition of new specimens is very limited, making it extremely difficult to obtain.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using compressed air to remove dust. Due to the extreme fragility and small size of the crystals, any mechanical contact, even with a soft brush, risks damaging them. Avoid contact with water and any chemicals. ## What to Avoid Ultrasonic cleaners, chemical agents, acids, and bases must be strictly avoided. The mineral is very soft and sensitive, so it should be protected from shocks, scratches, and sudden temperature changes. ## Storage Rudolfhermannite specimens should be stored exclusively in specialized "micromount" boxes, which protect them from dust and mechanical damage. They should be kept in stable conditions, away from moisture and direct sunlight.

External references

Sources

Read more