Wilkinsonite
Chemical formula: Na₄(Fe²⁺₈Fe³⁺₄)O₄[Si₁₂O₃₆]
Wilkinsonite is a very rare, black mineral from the aenigmatite group, discovered in Australia and named after geologist C.J. Wilkinson.
Properties
- Mohs hardness
- 5
- Streak
- Brown
- Density
- 0
- Fracture
- Conchoidal
- Transparency
- Translucent,Opaque
- Crystal system
- Triclinic
Diagnostic features
## Identification Field identification of wilkinsonite is practically impossible due to its rarity and appearance. Identification requires advanced laboratory methods such as chemical analysis (EDS) and X-ray diffraction (XRD). In a collection, it can be preliminarily identified based on its black color, mineral association, and confirmed provenance. ## Distinguishing from similar minerals Wilkinsonite can be confused with other black minerals from the aenigmatite group, such as aenigmatite or krinovite, as well as with more common minerals like hornblende, pyroxenes (e.g., augite), or ilmenite. Differentiation from members of its own group is possible only through chemical analysis. It is distinguished from other black minerals by, among other things, its lack of cleavage and specific occurrence environment. ## Crystal forms This mineral forms very small, tabular crystals, usually less than 1 mm in size. It most often occurs as inclusions in other minerals or rock.
Geological environment
## Genesis Wilkinsonite is a mineral of magmatic origin. It forms in the final stages of crystallization in alkaline, silica-undersaturated volcanic rocks, such as trachytes and phonolites. In its type locality (Warrumbungle Range), it occurs as a component of trachytes. ## Mineral associations This mineral co-occurs with other rare alkaline minerals. At the discovery site, it was found in association with sanidine, nepheline, analcime, aegirine, arfvedsonite, aenigmatite, lamprophyllite, and lorenzenite. ## Localities The only confirmed and thoroughly described occurrence of wilkinsonite in the world is its type locality: the Warrumbungle Range volcanic massif in New South Wales, Australia.
Rarity
Extremely rare
For collectors
## Quality criteria Due to the extreme rarity and microscopic size of its crystals, the main criterion for a specimen's value is the confirmed presence of wilkinsonite itself. The most desirable specimens are those where the crystals, though small, are as well-formed and visible against the host rock as possible. A rich association with other rare minerals also increases the scientific and collectible value of the specimen. ## Popular localities The only source of wilkinsonite specimens is its type locality in the Warrumbungle Range, Australia. Material from this location is practically unavailable on the collector's market.
Care and storage
## Cleaning Specimens containing wilkinsonite should be cleaned very carefully, preferably using a soft brush to remove dust. Due to its occurrence as inclusions in rock, wet cleaning is not recommended without knowing the properties of the host rock. ## What to avoid Avoid contact with chemicals, especially acids, which can damage both wilkinsonite and the surrounding minerals. Also avoid ultrasonic cleaners and sudden temperature changes. ## Storage Specimens should be stored in stable conditions, in separate, padded boxes to prevent abrasion and mechanical damage. It is best to keep them away from dust and direct sunlight, in a dry place.