Traskite

Chemical formula: Ba₂₁Ca(Fe₂+,Mn₂+,Ti₄+)₄(Ti₄+,Fe₂+,Mg)₁₂(Si₁₂O₃₆)(Si₂O₇)₆(O,OH)₃₀Cl₆·₁₄H₂O

Traskite is a very rare, complex titanium and barium silicate, forming tabular or prismatic crystals with a characteristic reddish-brown color.

## Characteristics Traskite is an exceptionally complex and rare mineral from the silicate group, chemically a hydrated barium, calcium, iron, and magnesium titanosilicate chloride. Its structure is one of the most complicated in the mineral world. It forms short, prismatic or tabular crystals with a hexagonal outline, rarely exceeding a few millimeters in length. It usually occurs as single crystals embedded in rock or as radial and divergent aggregates. ## Physical Properties The hardness of traskite on the Mohs scale is approximately 5, making it a mineral with moderate scratch resistance. It has a vitreous luster and is translucent to opaque. Its density is relatively high for a silicate, at 3.69 g/cm³, which is a result of the high barium content in its chemical composition. ## Colors and Varieties This mineral is characterized by a distinctive color palette, ranging from reddish-brown, through brown, to dark brown. No color or commercial varieties are distinguished. ## History and Name Traskite was first described in 1965 by J.T. Alfors, G.C. Stinson, R.A. Matthews, and A. Pabst. Its name honors John Boardman Trask (1824-1879), the first State Geologist of California, in recognition of his contributions to the geological research of that region. The type locality, from which the first described specimens originated, are the deposits in the Big Creek and Rush Creek area in Fresno County, California, USA. ## Applications Due to its extreme rarity, traskite 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: 5
Luster: Vitreous
Streak: Light brown
Density: 3.69
Cleavage: None
Fracture: Uneven
Transparency: Translucent to Opaque
Crystal system: Hexagonal

Diagnostic features

## Identification Diagnostic features of traskite include its reddish-brown color, vitreous luster, relatively high density, and characteristic form of short, hexagonal prisms. However, its paragenesis is key for identification – its occurrence in specific, barium-rich metamorphic rocks, in association with other rare barium minerals. ## Distinguishing from Similar Minerals Traskite can be confused with other rare minerals from the same locality. It is distinguished from reddish taramellite by its crystal form. It differs in color from fresnoite, which can be yellowish-green. Unlike white or colorless sanbornite and celsian, traskite is always colored. Identification often requires advanced studies, but for specimens from the type locality, the mineralogical context is very helpful. ## Crystal Forms Traskite crystallizes in the form of short, thick prismatic crystals, often with a distinct hexagonal cross-section. Crystals are usually small. It also occurs as aggregates with a radial or fan-like structure, where individual crystals diverge from a single center.

Geological environment

## Genesis Traskite is a metamorphic mineral. It forms under very specific conditions, in barium and manganese-rich silicate rocks (metamorphic sandstones) that have undergone contact metamorphism in the contact zone with intrusions of acidic igneous rocks. Its presence is an indicator of the unique chemistry of the parent rocks. ## Mineral Associations This mineral occurs in association with a whole suite of other rare barium and silicate minerals. Its most common associations include: sanbornite, quartz, celsian, walstromite, fresnoite, taramellite, diopside, pyrrhotite, and barite. ## Localities Traskite is an extremely rare mineral, known practically from only one locality in the world. This is its type locality – the Big Creek-Rush Creek area in Fresno County, California, USA, and specifically the Esquire No. 7 and No. 8 prospects. This is the only place where specimens of collector significance have been obtained.

Rarity

Very rare

For collectors

## Quality Criteria The most highly valued traskite specimens are those with well-formed, sharp, and lustrous crystals of an intense reddish-brown color. The size of the crystals is of great importance – even specimens a few millimeters in size are considered significant. Samples in which traskite occurs in rich association with other rare minerals from this locality, such as fresnoite or sanbornite, forming aesthetic and scientifically valuable compositions, are also highly desirable. ## Popular Localities The only source of valuable collector specimens of traskite is its type locality in Fresno County, California, USA. Specimens from this location are classics and adorn any advanced systematic collection or collection of rare minerals.

Care and storage

## Cleaning Traskite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used. Ultrasonic cleaners should be avoided, as they could damage the fragile structure of the mineral or its rock matrix. ## What to Avoid The mineral is sensitive to strong acids and other aggressive chemicals. It should be protected from impacts and scratches by harder minerals (e.g., quartz). There are no specific requirements regarding light or humidity exposure, but standard storage conditions are recommended. ## Storage It is recommended to store traskite specimens in separate, padded boxes or display cases to avoid contact with other minerals and prevent potential mechanical damage. This is especially important for delicate crystals embedded in a matrix.

Sources

IMA Mineral List (CNMNC)