Schairerite

Chemical formula: Na₂₁(S⁶⁺O₄)₇ClF₆

Schairerite is a rare, colorless or pale yellow sulfate halide, forming characteristic, sharply terminated dipyramidal crystals.

## Characteristics Schairerite is a complex sodium sulfate halide, occurring as well-formed, single crystals. Typical specimens take the form of sharp, hexagonal dipyramids, often elongated, resembling spindles. Crystals are usually small, reaching a few millimeters in length, although larger ones do occur. It can also be found in granular aggregates. It is a brittle mineral. ## Physical Properties Schairerite is characterized by a hardness of 3.5 on the Mohs scale. It has a vitreous luster and is transparent to translucent. Its density is approximately 2.61 g/cm³. ## Colors and Varieties This mineral is most often colorless, white, or takes on pale yellow hues. No color or commercial varieties are distinguished. ## History and Name Schairerite was discovered in 1931 in drill core samples from Searles Lake, California, USA. Its name commemorates John Frank Schairer (1904-1970), an American physical chemist from the Carnegie Institution for Science in Washington, who made significant contributions to the study of salt and silicate systems. ## Uses Schairerite has no industrial application. It is solely an object of interest for collectors specializing in rare minerals, especially those originating from evaporites.

Properties

Mohs hardness
3.5
Color
Colourless; colourless in transmitted light.
Luster
Vitreous
Streak
White
Density
2.612
Cleavage
Imperfect on {0001}
Fracture
Conchoidal
Transparency
Transparent,Translucent
Crystal system
Trigonal

Diagnostic features

## Identification The key diagnostic feature of schairerite is its characteristic crystal shape – sharply terminated, hexagonal dipyramids. Reaction to water (partial solubility) is also an important clue, although this is a destructive test. Its occurrence in association with other evaporite minerals in specific locations is a strong argument for its identification. ## Distinguishing from Similar Minerals Schairerite can be confused with other colorless or yellowish evaporite minerals of similar habit, such as some forms of gypsum or celestine. It differs from them by its lower hardness, characteristic crystal shape, and co-occurrence with minerals typical of Searles Lake, such as hanksite or trona. ## Crystal Forms Schairerite crystallizes in the form of simple, sharply terminated hexagonal dipyramids. Crystals are often elongated, with a spindle-like appearance. Less commonly, it forms granular aggregates.

Geological environment

## Genesis Schairerite is an evaporite mineral. It forms by precipitation from highly saline, alkaline waters in closed sedimentary basins (playa lakes) under arid climate conditions. It crystallizes directly from brines or within clay sediments saturated with salt solutions. ## Mineral Associations This mineral co-occurs with other evaporites, such as hanksite, trona, tychite, nahcolite, northupite, pirssonite, gaylussite, sulfohalite, and halite. It is most commonly found in association with minerals typical of the Searles Lake deposit. ## Localities The most important and classic locality for schairerite is Searles Lake in San Bernardino County, California, USA, from where the best specimens originate. It has also been identified in the Green River Formation in Sweetwater County, Wyoming (USA), and in the Koysha salt deposit in Ethiopia.

Rarity

Rare

For collectors

## Quality Criteria The most prized by collectors are sharp, well-formed, transparent, and undamaged crystals with a distinct, dipyramidal shape. Specimens with a visible, pale yellow color are also sought after. Aesthetic compositions of schairerite with other associated minerals, such as pink hanksite, are also highly valued. Crystal size is important, and specimens exceeding one centimeter are considered exceptional. ## Popular Localities Undoubtedly, the best and most famous schairerite specimens come from Searles Lake, California. This is the locality with which the mineral is inextricably linked, and collectors seek specimens from there.

Care and storage

## Cleaning Schairerite specimens should be cleaned with the utmost care. Due to its partial solubility in water, contact with liquids should be absolutely avoided. To remove dust, a soft brush or compressed air from a safe distance can be used. ## What to Avoid Contact with water, acids, and other chemicals, which can quickly damage or completely dissolve the crystals, must be strictly avoided. The mineral is sensitive to moisture, so it should not be stored in damp rooms. It is also brittle and susceptible to mechanical damage. ## Storage It is recommended to store specimens in a dry place, preferably in sealed containers or display cases with a desiccant (e.g., silica gel). Display should be in closed cabinets, away from sources of moisture and sudden temperature changes.

External references

Sources

Read more