Mcauslanite

Chemical formula: Fe<sup>2+</sup><sub>3</sub>Al<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>(PO<sub>3</sub>OH)F·18H<sub>2</sub>O

Mcauslanite is a very rare, hydrated iron and aluminum phosphate, forming characteristic, bluish-gray, spherical aggregates.

## Characteristics Mcauslanite is a very rare mineral from the phosphate group, chemically classified as a hydrated iron and aluminum phosphate with additional fluorine anions and hydroxyl groups. It occurs as small, spherical or hemispherical aggregates with a radial internal structure. The individual crystals forming the aggregates are platy or bladed, but rarely visible to the naked eye. Its typical appearance is spherical clusters up to 2 mm in diameter. ## Physical Properties This mineral is characterized by low hardness, 2 on the Mohs scale, which means it is very soft and susceptible to scratching. It has a vitreous luster. It is a light mineral, with a density of 2.25 g/cm³. It is transparent to translucent. ## Colors and Varieties The dominant and only recorded color of mcauslanite is bluish-gray. No varieties have been distinguished. ## History and Name The mineral was discovered in East Kemptville, Yarmouth County, Nova Scotia (Canada). It was described and approved as a new mineral species by the International Mineralogical Association (IMA) in 1986. Its name honors David Lloyd McAuslan (born 1925), a geologist from Nova Scotia, who first found this mineral. ## Uses Due to its extreme rarity and small size, mcauslanite has no industrial application. It is solely an object of interest for collectors specializing in rare minerals and scientists.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
White
Density
2.25
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Triclinic

Diagnostic features

## Identification The key diagnostic feature of mcauslanite is its unique form of occurrence: small (up to 2 mm), bluish-gray, spherical aggregates with a radial internal structure. The combination of this form, color, low hardness (2), and occurrence in a specific geological environment (granitic pegmatites) is characteristic. ## Distinguishing from Similar Minerals It can be confused with other secondary phosphates of similar appearance, such as wavellite, however, wavellite usually has a greenish tint and is harder (3.5-4). From other blue phosphates, like vivianite, it is distinguished by its spherical aggregate form and mineral associations. Final confirmation requires advanced analytical methods (XRD, EDS). ## Crystal Forms Mcauslanite crystals are very small, platy or bladed. They almost always occur as radial, spherical or hemispherical aggregates.

Geological environment

## Genesis Mcauslanite is a secondary mineral, formed in hydrothermal zones during the late stage of crystallization of phosphorus-rich granitic pegmatites. It forms in rock cavities and fissures as a result of the alteration of earlier phosphate minerals. ## Mineral Associations This mineral co-occurs with other phosphates, such as apatite, rockbridgeite, triplite, as well as with quartz, topaz, cassiterite, and mica (muscovite). ## Localities The only confirmed and described locality of mcauslanite in the world is its type locality - the East Kemptville tin mine in Yarmouth County, Nova Scotia, Canada.

Rarity

Extremely rare

For collectors

## Quality Criteria For collectors, the most important criterion is the size and development of the spherical aggregates. The most valued specimens are those where well-defined, undamaged spherical clusters are visible, clearly standing out from the host rock (matrix). Contrast with other associated minerals, such as quartz or topaz, also enhances the visual and collectible value of the specimen. ## Popular Localities The only source of mcauslanite specimens is its type locality in Nova Scotia, Canada. All specimens available on the collector's market originate from this single location.

Care and storage

## Cleaning Mcauslanite specimens should be cleaned with utmost care, using only a soft brush to remove dust. Due to its low hardness and potential reactivity, contact with water and any chemical agents should be avoided. ## What to Avoid Ultrasonic cleaners, chemical agents (acids, bases, solvents), and exposure to high temperatures, which can lead to dehydration and destruction of the mineral's structure, must be absolutely avoided. Protect from moisture and direct sunlight. ## Storage It is recommended to store specimens under stable conditions, in closed, padded "micromount" boxes, to protect them from mechanical damage, dust, and changes in humidity. It should not be stored with harder minerals that could scratch it.

Sources

Read more