Camgasite
Chemical formula: CaMgAs⁵⁺O₄(OH)·5H₂O
Kamgasite is a very rare calcium magnesium arsenate, forming colorless, tabular crystals and spherical aggregates.
Properties
- Mohs hardness
- 2
- Color
- Colourless
- Luster
- Vitreous
- Streak
- White
- Density
- 0
- Cleavage
- Perfect on {0001}
- Fracture
- Uneven
- Transparency
- Transparent,Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Identification of kamgasite under amateur conditions is practically impossible. It requires advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS). A visual, though non-specific, feature is the tiny, spherical aggregates composed of colorless, tabular crystals. ## Differentiation from similar minerals It can be confused with many other secondary arsenates or carbonates forming similar aggregates, such as pharmacolite, picropharmacolite, or hydromagnesite. Definitive differentiation is only possible based on chemical and crystallographic analysis. ## Crystal forms Kamgasite forms thin, tabular crystals with a hexagonal outline. These crystals most often occur as radial, spherical, or hemispherical aggregates.
Geological environment
## Genesis Kamgasite is a secondary mineral, formed as a result of hydrothermal processes in metamorphic deposits rich in manganese and iron. In its type locality (Långban), it occurs in fissures of dolomitic rocks, being a product of alterations of earlier arsenic minerals. ## Mineral associations This mineral co-occurs with other arsenates, such as berzeliite, manganoberzeliite, sarkinite, ecdemite, finnemanite, as well as with calcite and baryte. ## Localities The only confirmed occurrence of kamgasite in the world is the Långban mine, in the Filipstad region, Värmland province, Sweden. This is its type locality.
Rarity
Extremely rare
For collectors
## Quality criteria As a microscopic mineral, kamgasite is valued primarily for the mere fact of its presence on a specimen. Samples with well-formed, rich spherical aggregates, clearly contrasting with the host rock, are most highly rated. Confirmation of identification by a reputable laboratory is also important. ## Popular localities The only source of kamgasite specimens is the historic Långban mine in Sweden. All specimens available on the collector's market originate from this single location.
Care and storage
## Cleaning Due to its extreme rarity and delicacy, kamgasite specimens should only be cleaned if absolutely necessary, using compressed air to remove dust. Contact with water and any chemicals should be avoided. ## What to avoid Avoid all acids and detergents, which can damage the mineral. Specimens are very brittle and sensitive to mechanical damage. They should not be subjected to ultrasonic cleaning. ## Storage Kamgasite specimens, typically microscopic, should be stored in specialized "micromount" boxes, protecting them from dust, shocks, and humidity changes. Direct exposure to sunlight should be avoided, and they should be kept under stable room conditions.