Caminite
Chemical formula: Mg<sub>7</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>5</sub>(OH)<sub>4</sub>·H<sub>2</sub>O
A rare magnesium sulfate forming in the extreme conditions of hydrothermal vents on the ocean floor.
Description
## Characteristics Caminite is a hydrated magnesium hydroxysulfate, occurring as fine-grained, earthy, or porous aggregates. It typically forms white or colorless coatings and crusts. Individual crystals are microscopic in size and have a tabular or platy habit, giving the aggregates a dull, expressionless appearance. It is a brittle mineral. ## Physical Properties Caminite is relatively soft, with a Mohs hardness of 2.5, similar to a fingernail. Its luster is described as vitreous, and in compact aggregates, it can be dull or earthy. It is translucent, and its density is approximately 2.61 g/cm³. ## Colors and Varieties This mineral is usually white or colorless. No color varieties or trade names are distinguished. ## History and Name Caminite was first described in 1985 by Rachel M. Haymon and Miriam Kastner. Its name comes from the Spanish word *camino*, meaning "chimney" or "vent", which directly refers to its discovery location – "black smoker" type hydrothermal vents on the East Pacific Rise. ## Uses Caminite has no industrial applications. Its significance is purely scientific, as an indicator of processes occurring in submarine hydrothermal systems. It is an object of interest for collectors specializing in rare minerals.
Diagnostic features
## Identification Identification of caminite is primarily based on its unique occurrence environment – samples originating from submarine hydrothermal vents. It is a white, soft mineral forming fine-grained aggregates. Due to the lack of characteristic visual features, certain identification is almost exclusively possible using analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS). ## Distinguishing from Similar Minerals In the same environment, caminite can be confused with anhydrite or other light sulfates. Anhydrite is distinctly harder (3.5 on the Mohs scale). From carbonates, such as calcite, it is distinguished by its lack of reaction with hydrochloric acid. Differentiation from other rare magnesium sulfates requires specialized laboratory studies. ## Crystal Forms Caminite forms aggregates composed of microscopic, hexagonal platelets or tabular crystals. Well-formed crystals visible to the naked eye are not known.
Geological environment
## Genesis Caminite is a hydrothermal mineral. It forms under very specific conditions, crystallizing directly from hot (approx. 350°C), supersaturated solutions emanating from hydrothermal vents on the ocean floor. It forms in the zone of rapid mixing of these hot fluids with cold seawater, constituting one of the main components of "black smoker" vent walls. ## Mineral Associations It co-occurs with other minerals typical of hydrothermal vent deposits, such as anhydrite, sulfides (pyrite, chalcopyrite, sphalerite), and other rare sulfates. ## Localities The most important and classic locality for this mineral is the hydrothermal field on the East Pacific Rise, near 21°N, where it was discovered. Its presence has also been confirmed in other active hydrothermal systems, for example, on the Mid-Atlantic Ridge (TAG field). All known localities are located on the deep ocean floor and are inaccessible for standard collector exploration.
Rarity
Very rare
Collector aspects
## Quality Criteria As a microscopic mineral, caminite is not evaluated based on typical aesthetic criteria such as color or luster. The collector's value of a specimen primarily depends on its scientific significance. The most prized are rich aggregates of the mineral on a matrix, with accurately documented locality and analytically confirmed identity. Co-occurrence with other rare hydrothermal vent minerals adds significant value. ## Popular Localities Specimens come exclusively from scientific expeditions to submarine hydrothermal fields. The most well-known source is the type locality on the East Pacific Rise. This mineral is practically unavailable on the commercial market, and specimens are mainly found in institutional and specialized collections.
Care and storage
## Cleaning Caminite specimens are very delicate and potentially sensitive to water. They should only be dry-cleaned, using a soft brush or compressed air from a safe distance to remove dust. Contact with water, especially hot water, can lead to dissolution or damage to the mineral. ## What to Avoid Contact with water, acids, and other chemicals should be strictly avoided. The mineral is soft and brittle, so it must be protected from impacts and scratches. It is not sensitive to light, but extreme changes in temperature and humidity should be avoided. ## Storage It is recommended to store specimens in a dry place, preferably in a closed, padded "perky box". This protects the mineral from mechanical damage, dust, and changes in ambient humidity.