Bjarebyite

Chemical formula: BaMn<sup>2+</sup><sub>2</sub>Al<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>(OH)<sub>3</sub>

Bjarebyite is a rare phosphate group mineral, forming dark green, tabular crystals, valued by specialized collectors.

## Characteristics Bjarebyite is a complex barium, manganese, and aluminum phosphate. It occurs as small, tabular or bladed crystals, often forming radial or rosette-like aggregates. Its crystals rarely exceed a few millimeters in length. It is a brittle mineral with a characteristic dark green to almost black color. ## Physical Properties This mineral has a hardness of approximately 4 on the Mohs scale. It has a vitreous luster and is typically translucent, becoming opaque in thicker fragments. The density of bjarebyite is about 3.9 g/cm³. ## Colors and Varieties Bjarebyite occurs in shades from dark green to greenish-black. No distinct color or commercial varieties are recognized. ## History and Name The mineral's name comes from its discovery locality – the Bjärby quarry (formerly spelled Bjareby) in Sweden. It was first described in 1973 by P.B. Moore, P. Almen

Properties

Mohs hardness
4
Luster
Vitreous
Streak
Greenish-white
Density
3.9 - 3.93
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Translucent to opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Bjarebyite can be identified by its characteristic dark green color, tabular crystal habit, and occurrence in radial aggregates. It has a vitreous luster and a greenish-white streak. It reacts with acids. ## Distinguishing from Similar Minerals It can be confused with other green phosphates such as lazulite or wardite. It is distinguished from them by its specific crystal habit, hardness (approx. 4), and occurrence environment. Accurate identification often requires chemical (EDS) or X-ray (XRD) analysis. ## Crystal Forms It forms thin, tabular crystals with hexagonal or octagonal outlines, often grouped into rosette-like or radial aggregates. Crystals are usually small, reaching up to a few millimeters.

Geological environment

## Genesis Bjarebyite is a secondary mineral, forming in complex, granitic pegmatites rich in phosphates. It forms as a result of hydrothermal or metasomatic processes, replacing earlier phosphate minerals. ## Mineral Associations It often co-occurs with other rare phosphates such as wardite, lazulite, apatite, as well as quartz, muscovite, and albite. ## Localities The most important and classic locality, from which the best specimens originate, is the Bjärby quarry in the Värmland region of Sweden. It is also known from pegmatites in the Palermo No. 1 Mine and Charles Davis Mine in New Hampshire (USA) and from the Rapid Creek area in the Yukon Territory, Canada.

Rarity

Very rare

For collectors

## Quality Criteria The most valued by collectors are specimens with well-formed, sharp crystals forming aesthetic, rosette-like aggregates. Intense, dark green color and contrast with a light matrix rock are important. Due to the small size of the crystals, specimens larger than a centimeter are exceptionally rare and sought after. ## Popular Localities Classic and most desired specimens come from the type locality in Sweden (Bjärby). Well-formed crystals from pegmatites in New Hampshire, USA, are also highly valued.

Care and storage

## Cleaning Bjarebyite specimens should only be cleaned mechanically, using a soft brush and distilled water. Ultrasonic cleaners should be avoided, as they can damage the brittle crystals. ## What to Avoid The mineral is sensitive to acids, so contact with any chemicals should be avoided. It should also not be heated or exposed to sudden temperature changes. ## Storage It is recommended to store specimens in separate, padded boxes to prevent scratches and mechanical damage. It should be protected from dust and moisture.

Sources

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