Trembathite
Chemical formula: Mg<sub>3</sub>B<sub>7</sub>O<sub>13</sub>Cl
Trembathite is an extremely rare magnesium borate of the boracite group, characterized by high hardness and occurrence exclusively in Canada.
Description
## Characteristics Trembathite is a borate mineral belonging to the boracite group. Its chemical formula is Mg₃B₇O₁₃Cl, indicating that it is the magnesium analogue of boracite. It occurs as very small, anhedral (irregular) to subhedral (partially formed) grains, rarely exceeding 1 millimeter in size. It often forms rims or thin coatings on boracite crystals. It is a colorless or pale green mineral. ## Physical Properties Trembathite is characterized by very high hardness, measuring 8 on the Mohs scale, which is unusual for borates. Its luster is vitreous, and the mineral itself is transparent. The density of trembathite is approximately 2.96 g/cm³. It does not exhibit cleavage, and its fracture is conchoidal. ## Colors and Varieties This mineral is usually colorless, less frequently taking on pale green hues. No colored or commercial varieties are known. ## History and Name The name trembathite was given in honor of Lowell R. Trembath (1936–1990), a professor of mineralogy at the University of New Brunswick in Canada, in recognition of his contributions to research on minerals of the boracite group. The mineral was officially recognized by the International Mineralogical Association (IMA) in 1991, and its description was published in 1992. It was discovered in the Potash Corporation of Saskatchewan mine in New Brunswick. ## Applications Due to its extreme rarity and microscopic size, trembathite has no industrial or commercial applications. Its significance is purely scientific and collectible, as a unique representative of the boracite group.
Diagnostic features
## Identification Amateur identification of trembathite is impossible. Due to its microscopic size and similarity to other minerals of the boracite group, its recognition requires advanced analytical techniques, such as X-ray diffraction (XRD) or chemical microanalysis (EDS/WDS). Characteristic features, verifiable in the laboratory, include its chemical composition (dominance of magnesium), very high hardness (8 on the Mohs scale), and specific occurrence environment. ## Distinguishing from Similar Minerals The most similar mineral is boracite, from which trembathite is virtually impossible to distinguish visually. Boracite more often forms well-developed crystals. The ultimate distinction between the two minerals is based solely on chemical analysis – trembathite is the magnesium member, while iron predominates in boracite. It can also be confused with ericaite (the iron analogue). ## Crystal Forms Trembathite primarily occurs as irregular, anhedral grains (lacking their own faces) or subhedral grains (partially formed). It rarely forms visible crystalline shapes, and its crystals belong to the isometric system.
Geological environment
## Genesis Trembathite forms under specific conditions within marine evaporite deposits. Its crystallization occurs during diagenesis or low-grade metamorphism in an environment rich in boron, magnesium, and chlorine, which results from the evaporation of saline seawater. ## Mineral Associations This mineral occurs in close association with other evaporite minerals. It is most commonly found in association with boracite (on which it often grows), halite, and sylvite. ## Localities The only confirmed locality of trembathite in the world is its type locality – the Potash Corporation of Saskatchewan (PCS) mine near Penobsquis, Kings County, New Brunswick, Canada.
Rarity
Extremely rare
Collector aspects
## Quality Criteria For such a rare micromineral as trembathite, any specimen with analytically confirmed identity is valuable. Collectible value depends on the abundance of occurrence (quantity and size of grains on the rock matrix) and the quality of associated minerals. A specimen with visible, even partially formed (subhedral) crystals would be considered exceptional. ## Popular Localities All known trembathite specimens come from a single location in the world – the PCS mine in New Brunswick, Canada. This is the only locality from which collectors can acquire this mineral.
Care and storage
## Cleaning Trembathite specimens, due to their microscopic size and occurrence on delicate substrates (e.g., halite), should not be cleaned mechanically or chemically. If necessary, dust can be removed with compressed air. The mineral is insoluble in water. ## What to Avoid Contact with acids should be avoided. Although trembathite itself is hard and stable, associated minerals such as halite and sylvite are water-soluble and very sensitive to moisture. Therefore, specimens should be protected from water and high humidity. ## Storage It is recommended to store specimens in a dry and stable environment. The safest method is to place them in specialized "micromount" boxes, which protect against mechanical damage, dust, and moisture, and also prevent the loss of microscopic specimens.