Kleberite

Chemical formula: Fe₃+Ti₄+₆O₁₁(OH)₅

Kleberite is a discredited mineral name, now considered a mixture of titanium oxides (mainly anatase or rutile) and iron hydroxides.

## Characteristics Kleberite is a name given to a material that was ultimately discredited as a distinct mineral species. Specimens described as kleberite typically consist of fine-grained aggregates of anatase, less commonly rutile, with an admixture of iron hydroxides, such as goethite. It usually forms small, tabular crystals with hexagonal outlines, which often group into rosette-like aggregates. However, these forms are pseudomorphs after an unidentified primary mineral. ## Physical Properties Due to being a mixture, the physical properties of kleberite are variable. The hardness of the material was estimated at about 6 on the Mohs scale, and its density at 4.1 g/cm³. The luster was described as submetallic, and the material itself is opaque. These properties reflect the combined characteristics of its main components. ## Colors and Varieties Specimens historically referred to as kleberite range in color from reddish-brown to almost black. The streak is reddish-brown. No varieties are distinguished, as it is not an approved mineral. ## History and Name The name was given in honor of Will Kleber (1906-1970), a German crystallographer and mineralogist from Humboldt University in Berlin. The material was described from the Kropfmühl graphite mine in Bavaria (Germany). Initially considered a new mineral, it was eventually discredited by the International Mineralogical Association (IMA) after studies showed it to be a mixture rather than a homogeneous crystalline phase.

Properties

Mohs hardness: ~6
Luster: Sub-metallic
Streak: Red-brown
Density: 4.1
Fracture: Uneven
Transparency: Opaque

Diagnostic features

## Identification Identification of "kleberite" is practically impossible without advanced analytical methods, such as X-ray diffraction (XRD), which allows for the identification of its individual mineral components (anatase, rutile, goethite). A characteristic feature of historical specimens are small, pseudohexagonal, rosette-like aggregates with a reddish-brown color. ## Distinguishing from Similar Minerals It was originally confused with ilmenite or hematite due to its similar appearance and paragenesis. It differs from hematite by its streak (hematite has a cherry-red streak), and from ilmenite by the lack of magnetic properties. However, definitive differentiation requires confirmation that it is a polycrystalline mixture, not a single mineral. ## Crystal Forms It most often occurs as small, tabular crystals forming characteristic, radial aggregates resembling rosettes. These are pseudomorphs, meaning secondary forms that have retained the external shape of the primary, unknown mineral, which has been completely replaced by a mixture of oxides.

Geological environment

## Genesis Kleberite formed as a result of hydrothermal or low-grade metamorphic processes. In the type locality (Kropfmühl), it is a product of the alteration of an earlier, unknown titanium mineral within a graphite deposit. ## Mineral Associations In the type locality, it co-occurs with graphite, quartz, and various feldspars. ## Localities The only confirmed and historically significant occurrence of the material described as kleberite is the Kropfmühl graphite mine near Passau in the Bavarian Forest, Germany.

Rarity

Very rare

For collectors

## Quality Criteria As a material of mainly historical significance, the collector's value of kleberite is inextricably linked to its origin from the type locality (Kropfmühl, Germany). The most desirable specimens are those with well-formed, undamaged rosette-like aggregates, clearly embedded on a contrasting matrix (e.g., on graphite). The value of a specimen is enhanced by an old label confirming its historical character. ## Popular Localities The only source of collector specimens is the historical type locality in Kropfmühl, Bavaria.

Care and storage

## Cleaning Specimens can be safely cleaned with a soft, dry brush to remove dust. If necessary, distilled water may be used, but prolonged soaking should be avoided. After wet cleaning, the specimen should be thoroughly dried. ## What to Avoid Avoid contact with acids and strong chemicals, which could react with iron-containing components (e.g., goethite). Ultrasonic cleaning is not recommended, as it can damage delicate, rosette-like aggregates. ## Storage Kleberite is stable and does not require special storage conditions. It should be kept in a place not exposed to mechanical damage, preferably in a closed display box, to protect fragile crystalline forms.

Sources

IMA Mineral List (CNMNC)