Ophirite

Chemical formula: Ca<sub>2</sub>Mg<sub>4</sub>Zn<sup>2+</sup><sub>2</sub>Mn<sup>3+</sup><sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>(Fe<sup>3+</sup>W<sup>6+</sup><sub>9</sub>O<sub>34</sub>)<sub>2</sub>·46H<sub>2</sub>O

Ophirite is an extremely rare mineral from the tungstate group, with a very complex chemical composition, found exclusively in one location worldwide.

## Characteristics Ophirite is a mineral with an exceptionally complex chemical structure, belonging to the tungstate group. It forms aggregates of small, subhedral (partially developed) to anhedral (undeveloped) crystals, whose size does not exceed 0.2 mm. It usually occurs in the form of aggregates with a color ranging from dark reddish-brown to black. It is an opaque mineral, although its thinnest fragments may be translucent. ## Physical Properties The luster of ophirite is described as vitreous. Its hardness has not yet been studied. The density has also not been measured empirically, but only calculated based on its chemical composition and crystal structure, and is approximately 3.55 g/cm³. The streak, which is the color of the powdered mineral, is light brown. ## Colors and Varieties This mineral occurs in uniform colors, from dark reddish-brown to almost black. No color or commercial varieties are known. ## History and Name Ophirite was first described in 2001 by J.M. Hughes and his team. The mineral's name comes from its discovery location – the Ophir Hill Consolidated mine (also known as Ophir Mine) in the Ophir district, Utah, USA, which is its only known locality. ## Applications Due to its extreme rarity and microscopic crystal sizes, ophirite has no industrial application. It is solely an object of interest for specialized mineral collectors (especially microminerals) and scientific institutions.

Properties

Luster
Vitreous
Streak
Light brown
Density
3.55
Cleavage
None
Transparency
Opaque, Translucent in thin fragments
Crystal system
Triclinic

Diagnostic features

## Identification Identification of ophirite is impossible based on visual characteristics in field or amateur conditions. Due to the microscopic size of its crystals and its occurrence in aggregates, its recognition requires advanced analytical techniques, such as X-ray diffraction (XRD) and chemical composition analysis (e.g., EDS/WDS). A key clue is the specimen's origin from the type locality. ## Distinguishing from Similar Minerals It can be confused with other dark, opaque minerals co-occurring in the same rock. Certain differentiation from them is only possible with specialized laboratory tests. ## Crystal Forms Ophirite forms aggregates composed of very small, partially developed or completely undeveloped crystals. The maximum recorded size of a single crystal is 0.2 mm.

Geological environment

## Genesis Ophirite is a secondary mineral. It forms in fractures of quartz-muscovite rocks. Its genesis is associated with hydrothermal processes occurring in the oxidation zone of tungsten deposits. ## Mineral Associations This mineral occurs in association with scheelite, quartz, and muscovite. ## Localities The only confirmed locality of ophirite worldwide is the Ophir Hill Consolidated mine (Ophir Mine) in Ophir, Oquirrh Mountains, Tooele County, Utah, USA. This is its type locality.

Rarity

Extremely rare

For collectors

## Quality Criteria In the case of such a rare micromineral, the primary criterion for value is the confirmed presence of ophirite on the rock matrix itself. Specimens with richer crystal aggregates or those where the crystals are better (subhedrally) developed will be more highly valued. Clear association with other minerals, e.g., scheelite, also increases its value. ## Popular Localities The only source of specimens of this mineral is its type locality in Utah, USA. All specimens available on the collector's market come from this single mine.

Care and storage

## Cleaning As a mineral occurring in the form of microscopic crystals, ophirite requires exceptional caution. Mechanical cleaning (e.g., with a brush) is highly risky and can destroy the specimen. Only gentle rinsing in distilled water is permissible, followed by drying with compressed air from a safe distance. ## What to Avoid Ultrasonic cleaners, all chemical agents, acids, and detergents should be absolutely avoided. As a hydrated mineral, it is sensitive to high temperatures, which can lead to its dehydration and destruction of its structure. It should also be protected from direct sunlight. ## Storage Ophirite specimens should be stored in specialized micromount boxes, which protect them from dust, shocks, and mechanical damage. It is best to keep them in stable conditions, away from sources of heat and moisture.

External references

Sources

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