Brianroulstonite

Chemical formula: Ca₃B₅O₆(OH)₇Cl₂·₈H₂O

Brianroulstonite is a very rare, hydrated calcium borate, forming colorless, prismatic crystals with a vitreous luster.

## Characteristics Brianroulstonite is a complex, hydrated calcium borate with chlorine. It occurs as elongated, prismatic crystals that can reach up to 2 cm in length. It typically forms colorless or white, radial aggregates and rosettes. It is a transparent mineral with a vitreous luster. ## Physical Properties This mineral is characterized by its low hardness, measuring 2 on the Mohs scale, which means it is very soft and can be scratched with a fingernail. It has a density of 2.01 g/cm³. It is brittle and exhibits perfect cleavage in one direction. ## History and Name Brianroulstonite was discovered in the Potash Corporation of Saskatchewan mine in Penobsquis, New Brunswick, Canada. It was described in 1999 by Joel D. Grice, George W. Robinson, and Robert A. Gault. The mineral is named in honor of Brian V. Roulston (b. 1948), a Canadian geologist who first noticed this mineral and made significant contributions to understanding the geology of evaporites in New Brunswick. ## Uses Due to its extreme rarity and small crystal size, brianroulstonite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and for scientists.

Properties

Mohs hardness: 2
Luster: Vitreous
Streak: White
Density: 2.01
Cleavage: Perfect on {001}
Fracture: Uneven
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Brianroulstonite can be identified by its characteristic, elongated, prismatic crystals, often forming radial aggregates. Key features include vitreous luster, low hardness (2 on the Mohs scale), perfect cleavage, and water solubility. It is usually colorless or white. ## Distinguishing from Similar Minerals It can be confused with other colorless borates or sulfates found in evaporites, such as gypsum or halite. It differs from gypsum by its different crystal habit and perfect cleavage in one direction. It differs from halite by its crystal form (halite crystallizes in the isometric system) and lack of a salty taste. The water solubility test is a diagnostic feature. ## Crystal Forms Crystals are monoclinic, prismatic in habit, elongated along the b-axis. They often occur as radial or stellate aggregates, as well as single, well-formed crystals grown on other minerals.

Geological environment

## Genesis Brianroulstonite is a secondary mineral, forming in salt evaporite deposits. It forms as a result of the alteration of earlier borate minerals, such as hilgardite, in a water- and chlorine-rich environment. It occurs in caverns and fissures within sylvite and halite. ## Mineral Associations This mineral is associated with halite, sylvite, hilgardite, and other rare borates. ## Locations The only confirmed locality for brianroulstonite worldwide is its type locality - the Potash Corporation of Saskatchewan (now Nutrien) mine in Penobsquis, Kings County, New Brunswick, Canada.

Rarity

Extremely rare

For collectors

## Quality Criteria The most valued brianroulstonite specimens are those with well-formed, transparent, and undamaged crystals, forming aesthetic, radial aggregates. A contrasting matrix, e.g., composed of halite, also enhances the specimen's value. Due to its rarity, even small micromounts are sought after by collectors. ## Popular Localities The only source of brianroulstonite specimens is the mine in Penobsquis, Canada, making it extremely important for collectors specializing in mineral systematics or minerals from specific localities.

Care and storage

## Cleaning Brianroulstonite specimens should be cleaned with utmost care due to their brittleness and low hardness. Only gentle brushing with a soft brush is recommended to remove dust. Water should be avoided as the mineral is water-soluble. ## What to Avoid Contact with water, acids, and other chemicals that could damage or dissolve it must be absolutely avoided. The mineral is very soft, so it must be protected from scratches and impacts. It should not be exposed to high temperatures or humid air. ## Storage Brianroulstonite requires storage in dry conditions, preferably in a sealed, lidded display box away from sources of moisture. Due to its fragility, it should be stored in a separate compartment to avoid contact with harder minerals.

Sources

IMA Mineral List (CNMNC)