Salesite
Chemical formula: Cu²⁺(I⁵⁺O₃)(OH)
Salesite is a rare copper iodate, distinguished by characteristic, elongated crystals of an intense blue-green color.
Properties
- Mohs hardness
- 3
- Color
- Bluish-green; bluish green in transmitted light
- Luster
- Vitreous
- Streak
- Light green
- Density
- 4.72
- Cleavage
- on {101}
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Salesite can be identified by its characteristic, intense blue-green color, vitreous luster, and typical, elongated, prismatic crystals, often forming radial aggregates. It is relatively soft and heavy for its appearance. ## Distinguishing from Similar Minerals It can be confused with other secondary copper minerals of green color, such as brochantite, malachite, or dioptase. From brochantite, it is most often distinguished by a lighter shade and different crystal habit. Malachite usually forms botryoidal or fibrous aggregates and effervesces with hydrochloric acid, which salesite does not. Dioptase is much harder (hardness 5) and crystallizes in the trigonal system, forming short, rhombohedral crystals. ## Crystal Forms Salesite crystals are usually elongated along one axis (prismatic), often with a cross-section close to square. They occur as single, well-formed crystals or, more commonly, as radial, fan-shaped, or stellate aggregates.
Geological environment
## Genesis Salesite is a secondary mineral, forming in the oxidation (weathering) zones of copper deposits. Its formation requires the presence of iodine-rich solutions, which is a rare geological phenomenon. Iodine can originate from groundwater or from the weathering of older minerals containing this element. ## Mineral Associations It most often co-occurs with other secondary copper minerals, such as malachite, brochantite, libethenite, as well as iron oxides (goethite, hematite) and quartz. In the type locality (Chuquicamata), it was found in association with leightonite and belloite. ## Localities The most important and historical occurrence of salesite, from which the best specimens in the world originate, is the Chuquicamata copper mine in the Antofagasta region of Chile. This is its type locality. Beyond Chile, its presence has been noted in the Potrerillos mine, also in Chile, and in small quantities at the Dome Rock Copper Mine in South Australia.
Rarity
Very rare
For collectors
## Quality Criteria The most prized salesite specimens are characterized by sharp, well-terminated, and transparent crystals of intense, emerald-green or blue-green color. Rich groups of crystals forming aesthetic, radial or fan-shaped aggregates on a contrasting rock matrix are highly valued. The size of individual crystals, their luster, and lack of damage significantly increase their collector's value. ## Popular Localities By far the most sought-after specimens by collectors come from the Chuquicamata mine in Chile. This is the classic and practically only commercially significant locality for this mineral, and material from there sets the standard against which other finds are compared.
Care and storage
## Cleaning Salesite specimens should be cleaned very carefully, using only a soft brush to remove dust. Due to its softness and potential reactivity, avoid washing in water, and especially avoid using ultrasonics. ## What to Avoid Contact with acids and other chemicals, which can damage or dissolve the mineral, must be absolutely avoided. Salesite is sensitive to high temperatures and scratches. Prolonged exposure to intense sunlight may not be advisable. ## Storage It is recommended to store specimens in separate, padded boxes to protect them from mechanical damage and contact with harder minerals. It is best to keep it in stable conditions, away from moisture and direct sunlight.