Tausonite

Chemical formula: SrTi<sup>4+</sup>O<sub>3</sub>

Tausonite is a rare mineral from the oxide group, a natural analog of synthetic strontium titanate, valued for its high refractive index.

## Characteristics Tausonite is a strontium and titanium oxide belonging to the perovskite group. It occurs as very small, cubic or octahedral crystals, rarely exceeding 0.5 mm. They are usually embedded in the host rock. This mineral is a natural analog of synthetic strontium titanate, a material known in jewelry under the trade names "Fabulite" or "Diagem". ## Physical Properties Tausonite crystals are characterized by a very high, adamantine luster. It is a relatively hard and dense mineral. Its most distinguishing feature is an extremely high refractive index, which gives it exceptional brilliance, although natural crystals are usually too small to be fully appreciated. ## Colors and Varieties Tausonite is usually dark red, reddish-brown to almost black. It can be opaque, although thin fragments may be translucent in shades of red or brown. No varieties are distinguished. ## History and Name The mineral was first described in 1982 by A.A. Vorobiev and named after Lev Vladimirovich Tauson (1917-1989), a Russian geochemist and director of the Institute of Geochemistry in Irkutsk. It was approved by the International Mineralogical Association (IMA) in the same year. ## Applications Due to its extreme rarity and microscopic crystal sizes, tausonite has no industrial or commercial applications. It is solely an object of scientific and collecting interest for specialized micromineral collectors.

Properties

Mohs hardness
6-6.5
Luster
Adamantine
Streak
Brownish red
Density
5.12
Cleavage
Imperfect on {001}
Fracture
Conchoidal
Transparency
Translucent to opaque
Crystal system
Cubic

Diagnostic features

## Identification Identifying tausonite in the field is practically impossible due to the microscopic size of its crystals. Identification requires advanced laboratory methods, such as X-ray microanalysis (EDS/WDS) to confirm chemical composition (presence of strontium and titanium) and X-ray diffraction (XRD) to determine crystal structure. Visually, under a microscope, regular, cubic crystals with an adamantine luster can be observed. ## Distinguishing from Similar Minerals Under a microscope, tausonite can be confused with other minerals from the perovskite group, such as perovskite (CaTiO₃) or lueshite (NaNbO₃). Definitive differentiation is possible only through chemical analysis. From other dark minerals with regular crystals, such as magnetite or chromite, it is distinguished by the absence of magnetic properties and its characteristic composition. ## Crystal Forms Tausonite crystallizes in the isometric system, most often forming perfectly developed, single crystals in the form of cubes and octahedra, as well as their combinations. Crystals are usually very small, not exceeding 0.5 mm in size.

Geological environment

## Genesis Tausonite is a mineral of magmatic origin. It forms under specific conditions, in potassium- and titanium-rich ultramafic igneous rocks, such as syenites and carbonatites. It is one of the late minerals to crystallize from residual magma. ## Mineral Associations This mineral co-occurs with other rare alkaline minerals. Its typical associations include: calcite, dolomite, ankerite, phlogopite, barite, quartz, as well as minerals from the pyrochlore group and other rare titanates. ## Localities The most important and type locality for tausonite is the Murun Massif in the Aldan Shield, Siberia, Russia. This is one of the few confirmed locations worldwide where this mineral can be found. It has also been reported in carbonatites in Paraguay (Alto Paranaíba area).

Rarity

Very rare

For collectors

## Quality Criteria For tausonite, being a classic micromineral, the most important evaluation criteria are: the sharpness and definition of the crystal form, its size (the larger, the more valuable, although all are microscopic), and the aesthetic placement on the rock matrix. Luster and lack of damage also significantly increase the value of the specimen. Color contrast with the substrate is an additional advantage. ## Popular Localities By far the most prized and sought-after specimens by collectors come from the type locality – the Murun Massif in Siberia, Russia. This is practically the only source of specimens available on the collector's market.

Care and storage

## Cleaning Specimens containing tausonite, which are typically microcrystals on a rock matrix, should be cleaned very carefully. The safest method is to use compressed air to remove dust. If wet cleaning is necessary, a soft brush and distilled water can be used, followed by thorough drying of the specimen. ## What to Avoid Avoid contact with strong acids and chemicals that could damage both the microscopic tausonite crystals and the host rock. Ultrasonic cleaners should not be used, as they can cause small crystals to detach from the substrate. ## Storage Tausonite specimens are best stored in specialized micromount boxes, which protect them from dust and mechanical damage. Avoid exposure to moisture and sudden temperature changes.

External references

Sources

Read more