Calcjarlite
Chemical formula: Na<sub>2</sub>(Ca,☐)<sub>14</sub>(Mg,☐)<sub>2</sub>Al<sub>12</sub>F<sub>64</sub>(OH)<sub>4</sub>
Calcjarlite is a rare fluoride mineral, forming white, radial aggregates, known primarily from the unique cryolite deposit in Greenland.
Description
## Characteristics Calcjarlite is a complex fluoride of sodium, calcium, magnesium, and aluminum. It most commonly occurs as spherical or radial aggregates, composed of tiny, acicular or prismatic crystals. Individual crystals rarely reach visible sizes. Specimens are usually white or colorless and are opaque or at most translucent. ## Physical Properties This mineral is characterized by a Mohs hardness of 4, making it relatively soft. It has a vitreous luster on crystal surfaces. Its density is quite high for a fluoride, approximately 3.87 g/cm³. ## Colors and Varieties Calcjarlite is typically white, snow-white, or colorless. It does not form color varieties, nor are any trade names known for it. Variability in its appearance is mainly limited to the form and size of aggregates. ## History and Name The mineral was first described in 1933 by the Danish mineralogist O. B. Bøggild. Its name refers to its chemical composition – a high calcium content (Latin: *calx* - lime) – and its close structural and visual resemblance to jarlite, with which it often co-occurs. ## Uses Due to its extreme rarity, calcjarlite has no industrial applications. It is solely an object of scientific interest and a prized acquisition in advanced collections of rare and systematic minerals.
Diagnostic features
## Identification The characteristic features of calcjarlite are its forms of occurrence – white, radial or spherulitic aggregates. A key diagnostic clue is its origin from the unique geological environment of the cryolite deposit in Ivigtut, Greenland, and its co-occurrence with other rare fluorides. ## Distinguishing from Similar Minerals Calcjarlite is visually almost identical to jarlite. A definitive distinction between these two minerals is almost exclusively possible using advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS), which show the dominance of calcium over strontium in calcjarlite. It can also be confused with other white minerals from the Ivigtut deposit, such as stenonite or thomsenolite. ## Crystal Forms It forms acicular or finely prismatic crystals, which almost always occur as radial, fibrous, or spherulitic aggregates. Single, well-formed crystals are extremely rare.
Geological environment
## Genesis Calcjarlite is a hydrothermal mineral. It forms in the late stages of the evolution of granite pegmatites, rich in fluorine. Its classic locality is in altered zones within the unique cryolite deposit. ## Mineral Associations This mineral occurs in association with other rare fluorides characteristic of the Ivigtut deposit. These most commonly include jarlite, stenonite, weberite, thomsenolite, gearksutite, as well as fluorite, topaz, and cryolite. ## Localities The most important and historical locality for calcjarlite is the cryolite deposit in Ivigtut (now Ivittuut) in southwestern Greenland. This is its type locality, from which most research and collection material originates. The mineral has also been reported in several other locations worldwide, including Russia on the Kola Peninsula, but specimens from these localities are extremely rare.
Rarity
Very rare
Collector aspects
## Quality Criteria The collector's value of a specimen is primarily determined by the size and quality of the formed radial aggregates. Specimens rich in calcjarlite, with a distinct, spherical form, are more highly valued. The presence on a rock matrix and the association with other rare minerals from Ivigtut, such as stenonite or weberite, also add significant value. ## Popular Localities Specimens from the historical type locality – Ivigtut, Greenland – are by far the most valued and sought after by collectors. Material from this location is considered classic and referential for this species.
Care and storage
## Cleaning Calcjarlite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, it can be rinsed with distilled water. Ultrasonic cleaners should be avoided, as they can damage delicate aggregates. ## What to Avoid The mineral is susceptible to scratching by harder minerals (all with a hardness above 4). Contact with acids, which can damage it, should be avoided. It is stable at normal temperatures and under sunlight. ## Storage It is recommended to store calcjarlite specimens in separate, sealed boxes or display cases to protect them from dust and mechanical damage. It is best kept away from harder minerals to prevent scratching.