Jonlarsenite
Chemical formula: Al<sub>4</sub>Cu<sub>9</sub>
Jonlarsenite is an extremely rare mineral, an alloy of copper and aluminum, discovered as microscopic inclusions in quartz.
Properties
- Mohs hardness
- 4-5
- Luster
- Metallic
- Streak
- Black
- Density
- 6.45
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Tetragonal
Diagnostic features
## Identification Identifying jonlarsenite with the naked eye or a magnifying glass is impossible. Identification requires specialized laboratory equipment, such as a scanning electron microscope (SEM) with chemical composition analysis (EDS/WDS). In reflected light under a polarizing microscope, it is weakly anisotropic. ## Distinguishing from Similar Minerals As a microscopic inclusion, it can be confused with many other opaque minerals, such as sulfides, oxides, or other metal alloys. Definitive differentiation is only possible based on precise chemical analysis, which will show the presence of only copper and aluminum in appropriate proportions. ## Crystal Forms Jonlarsenite forms small, anhedral (lacking well-formed faces) grains with rounded or irregular shapes. No well-developed crystals have been observed.
Geological environment
## Genesis Jonlarsenite formed in the late stage of granite pegmatite crystallization. It occurs as inclusions in quartz, suggesting that it crystallized directly from a residual, metal-rich hydrothermal or magmatic phase under low oxygen activity conditions. ## Mineral Associations This mineral occurs directly as inclusions in quartz. In its pegmatite environment, other minerals such as microcline, albite, aegirine, zircon, and biotite have been found. ## Localities The only confirmed locality (type locality) of jonlarsenite in the world is the Stokkøya quarry, on the island of the same name, in the Langesundsfjord plutonic complex, in the Larvik region, Norway.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a jonlarsenite specimen is entirely dependent on the quality of the quartz matrix in which it is found. Since the mineral itself is invisible to the naked eye, its collector value is based on scientific confirmation of its presence. Specimens with an attached analytical certificate or from a reliable source (e.g., the discoverers) are most desirable. The size and aesthetics of the quartz specimen itself also play a role. ## Popular Localities The only source of specimens is the type locality – the Stokkøya quarry in Norway. Any specimen from this location is potentially valuable for specialized collectors of rare minerals and microminerals.
Care and storage
## Cleaning Given that jonlarsenite occurs as microscopic inclusions within much harder and more stable quartz, cleaning of the host specimen should be standard for quartz. Soapy water and a soft brush can be used. Aggressive mechanical methods that could damage the quartz surface should be avoided. ## What to Avoid The host specimen (quartz) is chemically resistant, but contact with hydrofluoric acid, which etches quartz, should be avoided. Jonlarsenite itself, as a metal alloy, may react with strong acids, so any chemical experiments should be avoided. ## Storage Specimens should be stored under stable conditions, away from dust and moisture. A standard collector's box or display cabinet is entirely sufficient. A detailed label indicating the presence of this rare mineral should be included.