How do I identify Tumchaite?

Tumchaite can be identified by its hardness of 4.5 on the Mohs scale, Colourless to white color. Look for these key characteristics when examining specimens.

What color is Tumchaite?

Tumchaite typically appears in Colourless to white. Color can vary depending on impurities and formation conditions.

How hard is Tumchaite?

Tumchaite has a hardness of 4.5 on the Mohs scale. This gives it moderate hardness.

Tumchaite

A variety of Minerals

What is Tumchaite?

Tumchaite, Na2(Zr,Sn)Si4O11•H2O, is a colorless to white monoclinic phyllosilicate mineral. It is associated with calcite, dolomite, and pyrite in the late dolomite-calcite carbonatites. It can be transparent to translucent; has a vitreous luster; and has perfect cleavage on {100}. Its hardness is 4.5, between fluorite and apatite. Tumchaite is isotypic with penkvilksite. The structure of the mineral is identified by silicate sheets parallel {100}, formed by alternation of clockwise and counterclockwise growing spiral chains of corner-sharing SiO4 tetrahedra. Tumchaite is named for the river Tumcha near Vuoriyarvi massif.

Tumchaite Market Value Calculator

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Tumchaite Localities Map

See where Tumchaite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.

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North ZoneCentral RidgeSouth Basin

Key Characteristics

Characteristics of Tumchaite

Tumchaite occurs as tabular monoclinic crystals, but other habits include massive and granular. The size of individual crystals is approximately 0.2 x 1.2 x 2.5 mm. It is colorless to white, transparent to translucent. The streak is white and the luster is vitreous. Cleavage on {100} is perfect, no parting is observed, and fracture is uneven as tumchaite is very brittle. The Mohs hardness is 4.5, between fluorite and apatite. The Vickers hardness test yielded 365 to 445- averaging 410- kg/mm with a 40 g load. The density, which was determined by flotation of the mineral using a dilute Clerici-H2O solution, was 2.78 (2) g/cm versus the 2.77 g/cm determined by the empirical formula.

Formation of Tumchaite

Tumchaite is found in carbonatites of the alkaline-ultramafic Vuoriyarvi massif, the Murmansk Region, Russia. This is located in the North Karelia on the north shore of the Vuoriyarvi lake and occupies an area of about 19.5 km. The mineral has been found as lens-like segregation of .5 x 1.0 x 1.5 cm in size in core sample from the bore hole. Tumchaite is associated with calcite, dolomite, a mineral of the serpentine group, and pyrite, and is formed during the hydrothermal alteration of carbonatites.

Composition of Tumchaite

Tumchaite is isotypic with penkvilksite-1M and is chemically related to vlasovite. The dominant structural feature of tumchaite is the silicate sheet [Si4O11] parallel to {100}, which can be considered as a result of condensation of the tetrahedral spiral chains running along [010] with six tetrahedra in the repeat unit. Adjacent spirals are oriented in alternate clockwise and counterclockwise ways. Tumchaite contains two symmetrically independent SiO4 tetrahedra: Si1 and Si2 have two and three bridging O atoms, respectively. The tetrahedral silicate sheets are connected by cationic octahedra with a disordered distribution of Zr and Sn (at 0, 1/2, 0), with the Zr/Sn ratio in these octahedra being 4. Figure 2 of Subbotin, et al., shows an illustration of this structure.