Gabrielsonite
Chemical formula: Pb²⁺Fe³⁺(As³⁺O₃)O
Gabrielsonite is a rare lead-iron arsenite, forming small, dark red-brown crystals with an adamantine luster.
Properties
- Mohs hardness
- 3.5
- Color
- Greenish-brown, black
- Luster
- Adamantine
- Streak
- Light brown
- Density
- 6.67
- Cleavage
- Perfect on {010}
- Fracture
- Irregular/Uneven,Sub-Conchoidal
- Transparency
- Translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Gabrielsonite can be identified by its characteristic dark red color, strong resinous or adamantine luster, and occurrence as small, tabular crystals. Key to identification is its association with the type locality — the Långban deposit — and specific mineral paragenesis. ## Distinguishing from Similar Minerals It can be confused with other rare, red or brown minerals from Långban, such as magnussonite or hematolite. Definitive differentiation requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS), due to the small size of the crystals. ## Crystal Forms It forms short, prismatic or thick tabular crystals, often with a nearly square cross-section. Crystals are usually very small, rarely reaching 1 mm.
Geological environment
## Genesis Gabrielsonite is a mineral of metamorphic origin. It forms in skarns, within metamorphosed iron and manganese ore deposits. Its formation is associated with hydrothermal or pneumatolytic activity, which mobilizes lead and arsenic under specific chemical conditions. ## Mineral Associations This mineral co-occurs with other rare minerals typical of the Långban deposit. It is most often found in association with magnussonite, hematolite, hausmannite, native lead, calcite, and various minerals from the phlogopite group. ## Localities The only confirmed and described occurrence of gabrielsonite in the world is its type locality — the Långban deposit, in Filipstad Municipality, Värmland County, Sweden. This is a classic locality for many rare and unique minerals.
Rarity
Very rare
For collectors
## Quality Criteria The quality of a gabrielsonite specimen is primarily determined by the size and quality of crystal formation. The most prized specimens are those with distinct, well-formed crystals of intense color and strong luster, set on a contrasting rock matrix. Due to its extreme rarity, any authentic specimen, even in the form of microscopic crystals, holds significant value for specialized collectors. ## Popular Localities The only source of gabrielsonite specimens is the historic Långban deposit in Sweden. The mine has long been inactive, and new specimens are virtually unavailable on the market, originating solely from old collections.
Care and storage
## Cleaning Gabrielsonite specimens should be cleaned only with great care, using a soft brush to remove dust. Due to its brittleness and rarity, wet cleaning, and especially ultrasonic cleaning, should be avoided. ## What to Avoid Contact with acids and other chemicals that could damage it must be absolutely avoided. The mineral is brittle, so it should be protected from impacts and vibrations. It should not be heated or exposed to sudden temperature changes. ## Storage Gabrielsonite specimens, usually microscopic in size, are best stored in specialized "micromount" boxes, which protect them from mechanical damage and dust. Exposure to direct sunlight should be avoided, although there is no evidence of fading.