Lasnierite

Chemical formula: (Ca,Sr)(Mg,Fe<sup>2+</sup>)<sub>2</sub>Al(PO<sub>4</sub>)<sub>3</sub>

Lasnierite is a very rare phosphate mineral of the alluaudite group, found in granitic pegmatites in Canada.

## Characteristics Lasnierite is an extremely rare mineral of the alluaudite group, occurring as small, anhedral (irregularly shaped) grains not exceeding 200 micrometers in size. These grains are most often intergrown with other minerals, mainly arrojadite-(KFe). Due to its microscopic size and mode of occurrence, its visual features are difficult to observe without specialized equipment. ## Physical Properties The mineral is characterized by a vitreous luster. It is brittle, and its Mohs hardness is estimated at 5. The density calculated based on the chemical formula and unit cell parameters is 3.55 g/cm³. ## Colors and Varieties Lasnierite is pale yellow to yellowish-green in color. No varieties have been distinguished. ## History and Name The mineral was discovered in the Tanco pegmatite in Bernic Lake, Manitoba, Canada. It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2007 (IMA2007-030). The name honors Roger Lasnier (born 1943), a French mineral collector and amateur researcher who specialized in the mineralogy of the Armorican Massif pegmatites in France and was a co-discoverer of several new minerals.

Properties

Mohs hardness
5
Luster
Vitreous
Streak
Pale yellow
Density
3.55
Cleavage
Good on {100}
Fracture
Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of lasnierite is only possible using advanced laboratory methods, such as X-ray microanalysis (EDS/WDS) combined with X-ray diffraction (XRD). Under collector or field conditions, its identification is impossible due to the microscopic size of the grains and its similarity to other phosphates. ## Distinguishing from Similar Minerals Lasnierite is visually indistinguishable from other minerals of the alluaudite and arrojadite groups with which it coexists. Chemical analysis is required to differentiate it from ferroalluaudite, alluaudite, or arrojadite-(KFe) based on its calcium, magnesium, and aluminum content. ## Crystal Forms This mineral exclusively forms anhedral, irregular grains up to 200 µm in size, usually intergrown with other minerals.

Geological environment

## Genesis Lasnierite forms in complex, lithium-cesium-tantalum (LCT-type) granitic pegmatites. It is a secondary mineral that forms as a result of metasomatic or hydrothermal alteration of earlier phosphates, such as arrojadite-(KFe). This process occurs in the presence of aluminum-enriched fluids. ## Mineral Associations This mineral occurs in close association with arrojadite-(KFe), in which it forms inclusions. It also coexists with other phosphates, such as apatite, wyllyeite, as well as quartz, microcline, and spodumene. ## Localities The only confirmed locality for lasnierite in the world is its type locality – the Tanco pegmatite, located at Bernic Lake in Manitoba, Canada. This is one of the most mineralogically diverse pegmatite deposits in the world.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, lasnierite is not evaluated according to typical collector criteria such as size, color, or crystal form. Its value is purely scientific and systematic. For collectors specializing in rare minerals or "micromounts," the only criterion is possessing an analytically confirmed specimen from the type locality. The visual appeal of the entire specimen depends on the associated minerals.

Care and storage

## Cleaning Due to its microscopic size and occurrence as inclusions within other minerals, mechanical or chemical cleaning of individual lasnierite grains is practically impossible and not recommended. The host specimen should be cleaned using methods appropriate for the dominant minerals (e.g., arrojadite), typically using a soft brush and distilled water. ## What to Avoid Avoid contact with strong acids, which can damage the mineral. The specimen should not be exposed to ultrasound or sudden temperature changes. As a phosphate mineral, it may be sensitive to certain chemicals. ## Storage Specimens containing lasnierite should be stored in stable conditions, away from dust, humidity, and direct sunlight. It is best to keep them in sealed collector's boxes to protect them from mechanical damage and contamination.

Sources

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