Rotemite

Chemical formula: Ca₄Cr³⁺₂(OH)₁₂Cl₂·4H₂O

Rotemite is a very rare mineral from the hydrotalcite supergroup, distinguished by its pale, bluish-violet coloration and occurrence in the Hatrurim Formation in Israel.

## Characteristics Rotemite is a hydrated calcium chromium hydroxychloride belonging to the hydrotalcite supergroup. It forms small, hexagonal tabular crystals, which typically occur as rosetted or spherulitic aggregates. Its characteristic feature is a delicate, pale bluish-violet color. Due to its extreme rarity and small crystal size, it is a mineral known primarily in scientific and specialized circles. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 2.5-3, placing it between calcite and gypsum. It has a low density, approximately 2.18 g/cm³. It exhibits a vitreous luster. It is transparent to translucent. It possesses perfect cleavage in one plane, which is typical for minerals with a layered crystal structure. ## Colors and Varieties Rotemite occurs in a uniform, characteristic shade of pale bluish-violet. No color varieties or commercial variants have been described. ## History and Name The mineral's name comes from its discovery location – the Rotem Industrial Complex, situated near the Hatrurim Formation in Israel. It was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 2013. Its detailed scientific description was published in 2015. ## Uses Due to its extreme rarity, small size, and scientific significance, rotemite is solely an object of collector and research interest. It has no industrial applications.

Properties

Mohs hardness
2.5-3
Luster
Vitreous
Streak
pale light-purple
Density
2.18
Cleavage
{0001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Trigonal

Diagnostic features

## Identification Rotemite can be identified by its unique, pale bluish-violet color, hexagonal crystal outline, tabular habit, and characteristic rosetted aggregates. Its low hardness (2.5-3) and perfect cleavage are also important diagnostic features. However, verification of the location is crucial – this mineral originates exclusively from the Hatrurim Formation. ## Distinguishing from Similar Minerals Due to its specific color and form, it is difficult to confuse with other minerals, especially when considering its paragenesis. Some other minerals from the hydrotalcite supergroup may have a similar structure but usually differ in color. ## Crystal Forms Rotemite crystals are tabular, with a hexagonal outline. Most often, they form small, radial aggregates in the shape of rosettes or spherulitic clusters, reaching up to 0.2 mm in diameter.

Geological environment

## Genesis Rotemite forms under specific conditions of low-temperature alteration within pyrometamorphic rocks of the Hatrurim Formation. It is a product of hydrothermal processes occurring in calcium-rich rocks that have previously been subjected to high temperatures. ## Mineral Associations This mineral occurs in association with other rare minerals of the Hatrurim Formation, such as calcite, aragonite, bentorite, ye'elimite, and various minerals from the ettringite group. ## Localities The only confirmed locality of rotemite in the world is its type locality – the Halamish quarry in the Hatrurim Basin, Israel. This site is known for the occurrence of many unique and rare minerals formed during pyrometamorphism.

Rarity

Extremely rare

For collectors

## Quality Criteria The most valuable rotemite specimens are those with well-formed, distinct rosetted aggregates with an intense coloration, for this mineral. Contrast with the rock matrix and absence of mechanical damage are also important. Due to the microscopic size of the crystals, specimens are primarily evaluated under magnification. ## Popular Localities The only source of rotemite specimens is its type locality in Israel. All materials available on the collector's market originate from this single location.

Care and storage

## Cleaning Rotemite specimens should be cleaned with the utmost care, using only compressed air to remove dust. Due to its softness and potential reactivity, contact with water, and especially with acids and detergents, should be avoided. ## What to Avoid Avoid cleaning in ultrasonic cleaners, chemical cleaning, and sudden temperature changes. The mineral is soft and brittle, so it must be protected from scratches and impacts. Prolonged exposure to strong sunlight may be potentially harmful, although there are no detailed studies on this topic. ## Storage It is recommended to store rotemite specimens in stable conditions, in closed display boxes, away from dust, moisture, and direct sunlight. It is best to keep it in a separate container to avoid contact with harder minerals that could damage it.

External references

Sources

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