Lourenswalsite

Chemical formula: (K,Ba)<sub>2</sub>Ti<sup>4+</sup><sub>4</sub>(Si,Al)<sub>6</sub>O<sub>14</sub>(OH)<sub>12</sub>

Lourenswalsite is a very rare silicate mineral, forming characteristic, thin flakes with a pearly luster and a golden-yellow color.

## Characteristics Lourenswalsite is a complex titanium, potassium, and barium silicate, belonging to the group of rare minerals. It occurs as small, thin, platy crystals with a hexagonal outline. These flakes are flexible and elastic. It most commonly forms scaly aggregates, rosettes, or radial clusters. Its appearance is typical of mica group minerals, to which it is related. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of approximately 2.5. It is characterized by perfect, unidirectional cleavage, allowing for easy separation of thin flakes. The luster on cleavage surfaces is distinctly pearly, while on other surfaces it can be dull or earthy. It is translucent, and its density is calculated to be 3.13 g/cm³. ## Colors and Varieties Lourenswalsite has a characteristic golden-yellow or brownish-yellow color. There are no named color varieties or commercial varieties. ## History and Name The mineral was first described in 1987 by A. D. Khalilov, A. P. Khomyakov, and A. V. Mokhov. Its name honors Lourens (Lou) Wals, a Dutch mineralogist and collector, in recognition of his contribution to the study of the mineralogy of the Murun Massif in Russia, where the discovery was made. ## Applications Due to its extreme rarity, lourenswalsite has no industrial applications. It is solely an object of scientific interest and a prized acquisition for specialized collectors of rare minerals.

Properties

Mohs hardness
2.5
Luster
Pearly
Streak
Pale yellow
Density
3.13
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Features that allow for the identification of lourenswalsite include its golden-yellow color, strong pearly luster on cleavage surfaces, and the form of thin, flexible flakes with a pseudohexagonal outline. Its unique occurrence environment is also a key indicator. ## Distinguishing from Similar Minerals Lourenswalsite can be confused with other micas of similar color, such as phlogopite or some varieties of muscovite. It is distinguished from them by its specific chemical composition (high titanium and barium content), which can only be confirmed by advanced analysis. In field conditions, the most important distinguishing criterion is the mineral paragenesis typical of the Murun Massif. ## Crystal Forms Crystals have a tabular or platy habit, often with a hexagonal outline. They usually occur as radial aggregates, rosettes, or scaly clusters on the host rock.

Geological environment

## Genesis Lourenswalsite is a magmatic mineral, crystallizing in the late stages of the formation of specific, silica-undersaturated alkaline rocks, such as carbonatites. ## Mineral Associations This mineral occurs in association with other rare minerals typical of its formation environment. It most commonly co-occurs with aegirine, microcline, daqingshanite-(Ce), and calcite. ## Localities The only known and confirmed locality of lourenswalsite, which is also its type locality, is the Murun Massif in the Sakha Republic (Yakutia) in Siberia, Russia.

Rarity

Very rare

For collectors

## Quality Criteria The most highly prized lourenswalsite specimens are those with well-formed, large rosette aggregates of intense, golden-yellow color, contrasting with the rock matrix. The presence of other rare associated minerals is also important, as it increases the scientific and collector value of the specimen. ## Popular Localities The only source of collector specimens is the Murun Massif in Russia. Material from this locality is extremely difficult to obtain and appears on the market very rarely.

Care and storage

## Cleaning Lourenswalsite specimens are very delicate and should be handled with utmost care. For dust removal, it is best to use a soft, dry brush or a stream of compressed air from a safe distance. Wet cleaning should be avoided. ## What to Avoid This mineral is susceptible to mechanical damage due to its low hardness and perfect cleavage. Contact with water, chemical agents, and ultrasonic cleaners, which could irreversibly damage the delicate flakes, must be strictly avoided. ## Storage It is recommended to store specimens in closed, padded "micromount" boxes to protect them from dust, light, and mechanical damage. It should not be displayed in areas exposed to vibrations or direct sunlight.

Sources

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