Shuiskite-(Cr)
Chemical formula: Ca<sub>2</sub>Cr<sup>3+</sup>Cr<sup>3+</sup><sub>2</sub>[SiO<sub>4</sub>][Si<sub>2</sub>O<sub>6</sub>(OH)](OH)<sub>2</sub>O
A complex calcium chromium silicate, distinguished by its intense emerald-green color and extreme rarity.
Description
## Characteristics Shuiskite-(Cr) is a sorosilicate mineral belonging to the epidote group. It forms fine-grained aggregates, veins, and clusters composed of small, prismatic crystals, reaching up to 1 cm in length. Its most characteristic feature is its vivid, emerald-green color, resulting from a high chromium content. ## Physical Properties This mineral has a hardness of approximately 6 on the Mohs scale. It exhibits a vitreous luster and is translucent. The calculated density is 3.46 g/cm³, but this has not been empirically confirmed due to the scarcity of research material. ## Colors and Varieties Shuiskite-(Cr) occurs exclusively in one characteristic color – emerald-green. No color varieties or commercial forms are known. ## History and Name The mineral was described in 1980 by a group of Russian researchers (V. V. Smirnova, V. A. Malyishev, L. K. Vostroknutova, N. I. Eryomin). Its name honors Vadim Petrovich Shuisky (1935–), a Russian geologist and paleontologist specializing in Paleozoic algae and stromatoporoids in the Urals. ## Applications Due to its extreme rarity, shuiskite-(Cr) has no industrial applications. It is solely an object of scientific interest and a valuable acquisition for advanced systematic collections.
Diagnostic features
## Identification The key diagnostic feature is its intense emerald-green color combined with its specific occurrence environment – veins cutting chromite ores in serpentinites. Confirmation of identity requires advanced analytical methods (e.g., XRD, EDS) due to its similarity to other chromium minerals. ## Distinguishing from Similar Minerals Shuiskite-(Cr) can be confused with other green chromium minerals. It is distinguished from uvarovite (garnet) by its lower hardness and monoclinic crystal system (uvarovite is isometric and harder, 6.5-7.5). It differs from chromian clinochlore (kammererite) by its significantly higher hardness (kammererite has a hardness of 2-2.5). It is distinguished from pargasite by the absence of the typical amphibole cleavage angle. ## Crystal Forms It most commonly occurs as fine-grained, massive aggregates and as veins. Less frequently, it forms well-developed, short, prismatic crystals.
Geological environment
## Genesis Shuiskite-(Cr) is a hydrothermal mineral. It forms within chromite deposits associated with ultramafic rocks, such as serpentinites. It crystallizes in the late stage of metamorphic processes, filling fissures and fractures in the chromite ore. ## Mineral Associations This mineral occurs in direct association with chromite, calcite, quartz, and minerals from the serpentine group. ## Localities The only confirmed locality for shuiskite-(Cr) in the world is its type locality – the Saranovskoe (Sarany) Mine in the Perm Krai, Middle Urals, Russia.
Rarity
Extremely rare
Collector aspects
## Quality Criteria For such a rare mineral, the main criterion of value is its mere presence and the confirmation of its identity. Specimens where shuiskite-(Cr) forms rich, intensely colored aggregates contrasting with a dark chromite matrix are more highly prized. The presence of small, well-formed crystals significantly increases the value of the specimen. ## Popular Localities All known collector specimens originate from a single locality – the Sarany mine in the Russian Urals. Material from this locality is extremely difficult to acquire.
Care and storage
## Cleaning Specimens should only be cleaned mechanically, using a soft brush to remove dust. If necessary, distilled water can be used, followed by thorough drying of the specimen. Ultrasonic cleaners should be avoided, as they can damage delicate aggregates. ## What to Avoid The mineral should be protected from contact with strong acids and bases. It should not be subjected to rapid temperature changes. Prolonged exposure to direct sunlight is not recommended, although there is no data on its fading. ## Storage Shuiskite-(Cr) specimens are best stored in closed membrane boxes or display cases, which protect them from dust, moisture, and mechanical damage.