Janhaugite

Chemical formula: Na₃Mn₂+₃Ti₄+₂(Si₂O₇)₂(O,OH,F)₄

Janhaugite is a rare silicate from the wöhlerite group, forming reddish-brown, tabular crystals, valued by collectors specializing in pegmatite minerals.

## Characteristics Janhaugite is a complex sodium, manganese, and titanium silicate belonging to the wöhlerite group. It occurs as small, tabular or bladed crystals, often grouped into radial or randomly oriented aggregates. Crystals are usually well-formed, not exceeding a few millimeters in size. ## Physical Properties This mineral is characterized by a hardness of approximately 5 on the Mohs scale. It has a vitreous, slightly resinous luster. It is a relatively dense mineral, with a density of 3.56 g/cm³. Crystals are usually translucent at the edges, and opaque in thicker sections. ## Colors and Varieties Janhaugite has a characteristic, uniform color ranging from brownish-red to reddish-brown. No color or commercial varieties have been distinguished. ## History and Name The mineral was first described in 1981 by Raade, Rømming, Land, and Husdal. Its name honors Jan Haug (1910–1980), a Norwegian mineral collector who first found this mineral in a pegmatite on Gjerdingen mountain in Norway. This locality is considered the type locality (place of first discovery). ## Uses Janhaugite has no industrial applications. It is solely an object of interest for collectors of rare minerals and a subject of scientific research.

Properties

Mohs hardness: 5
Luster: Vitreous to resinous
Streak: Light brown
Density: 3.56
Cleavage: Good on {100}
Fracture: Uneven
Transparency: Translucent to opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Janhaugite is identified by its characteristic reddish-brown color, tabular crystal habit, vitreous luster, and specific occurrence environment – nepheline syenite pegmatites. A hardness of approximately 5 and relatively high density are additional indicators. ## Distinguishing from Similar Minerals It can be confused with other reddish-brown silicates from pegmatites, such as eudialyte, lavenite, or some garnets. It is distinguished from eudialyte by its crystal habit (eudialyte often forms more isometric grains) and higher hardness. Distinguishing it from lavenite and other minerals of the wöhlerite group requires advanced analytical methods, such as chemical analysis (EDS/WDS) or X-ray diffraction (XRD). ## Crystal Forms Crystals are typically tabular, flattened parallel to the {100} plane, and exhibit a bladed habit. They often form radial or disordered aggregates and clusters.

Geological environment

## Genesis Janhaugite is an igneous mineral, crystallizing in the late stages of nepheline syenite pegmatite evolution. It forms in an environment rich in sodium, manganese, titanium, and fluorine. ## Mineral Associations This mineral co-occurs with other rare pegmatite minerals. At the type locality (Gjerdingen, Norway), it was found in association with albite, microcline, nepheline, aegirine, lorenzenite, lavenite, manganoneptunite, eudialyte, and apophyllite. On the Kola Peninsula, it is associated with aegirine, lorenzenite, murmanite, lomonosovite, and villiaumite. ## Localities Janhaugite is an extremely rare mineral, known from only a few localities worldwide. The most important occurrences are: - **Norway:** Gjerdingen in Nordmarka near Oslo (type locality). - **Russia:** Khibiny and Lovozero Massifs on the Kola Peninsula.

Rarity

Very rare

For collectors

## Quality Criteria Specimens with well-formed, sharp crystals of intense, reddish-brown color are most valued by collectors. Rich aggregates of crystals on a contrasting matrix (e.g., on white albite or nepheline) are also highly regarded. Due to the rarity of the mineral, even small microcrystals are sought after. ## Popular Localities Specimens from the type locality in Norway and from the alkaline massifs of the Kola Peninsula in Russia are the most desirable, as they come from classic and best-studied occurrences of this mineral.

Care and storage

## Cleaning Specimens should only be cleaned mechanically, using a soft, dry brush or paintbrush to remove dust. Due to its rarity and potential reactivity, contact with water and all chemical agents should be avoided. ## What to Avoid Ultrasonic cleaners should be avoided, as they can damage delicate crystals. The mineral should be protected from contact with acids and other chemicals. There is no detailed data on its sensitivity to light or temperature, but standard caution is recommended. ## Storage Janhaugite specimens are best stored in stable conditions, in sealed collector boxes that protect against dust and mechanical damage. Due to the small size of the crystals, "micromount" type boxes are worth considering.

Sources

IMA Mineral List (CNMNC)