Reedmergnerite

Chemical formula: NaBSi<sub>3</sub>O<sub>8</sub>

Reedmergnerite is a rare sodium borosilicate, a boron analogue of albite, distinguished by its occurrence in unusual, alkaline rocks.

## Characteristics Reedmergnerite is a rare mineral from the silicate group, belonging to the feldspar family. It is the boron analogue of common albite, where boron replaces aluminum in the crystal structure. It typically forms colorless or white, vitreous grains, often small in size, occurring in intergrowths with other minerals. Its crystals, when well-formed, resemble feldspar crystals, such as albite, and may exhibit characteristic twinning. ## Physical Properties This mineral is characterized by a hardness of approximately 6 on the Mohs scale, which is typical for feldspars. It has a vitreous luster and is transparent to translucent. Its density is about 2.57 g/cm³, making it slightly less dense than quartz. It exhibits perfect cleavage in two directions, which is also a characteristic feature of feldspars. ## Colors and Varieties Reedmergnerite is most often colorless or white. No named color varieties or commercial varieties are distinguished for it. ## History and Name The mineral's name honors two geologists from the United States Geological Survey (USGS), John C. Reed Jr. (1905–1992) and Frank S. Mergner (1916–1956). It was first described in 1955 based on material from the Green River Formation in Duchesne County, Utah, USA. ## Uses Due to its extreme rarity, reedmergnerite has no industrial applications. It is solely an object of scientific interest and a prized acquisition for advanced systematic and rare mineral collections.

Properties

Mohs hardness
6
Luster
Vitreous
Streak
White
Density
2.57
Cleavage
Perfect on {001}, good on {010}
Fracture
Uneven to conchoidal
Transparency
Transparent to translucent
Crystal system
Triclinic

Diagnostic features

## Identification Identification of reedmergnerite in the field is practically impossible without advanced analytical methods. In a collection, it can be tentatively recognized based on its association with other rare alkaline minerals from the Green River Formation. The characteristic vitreous luster and crystal habit similar to albite are clues, but definitive confirmation requires chemical analysis (EDS) or X-ray diffraction (XRD) to detect boron and sodium and confirm the structure. ## Distinguishing from Similar Minerals Reedmergnerite is visually almost identical to albite and other plagioclase feldspars. It can also be confused with quartz, especially when it occurs as anhedral grains. It differs from albite by the presence of boron instead of aluminum, which is undetectable without specialized equipment. It differs from quartz by the presence of perfect cleavage in two directions. ## Crystal Forms Reedmergnerite crystallizes in the triclinic system. It forms tabular or prismatic crystals, often twinned according to laws typical for feldspars (e.g., albite law). Most often, however, it occurs as irregular, anhedral grains embedded in the host rock.

Geological environment

## Genesis Reedmergnerite is a hydrothermal or authigenic mineral, forming in specific, highly alkaline and boron-rich environments. It forms at low temperatures in sedimentary rocks, such as shales and marls, which have been altered by sodium- and boron-rich solutions. ## Mineral Associations This mineral co-occurs with other rare evaporite and authigenic minerals. In its type locality (Green River Formation), its associations include shortite, eitelite, leucosphenite, searlesite, loughlinite, analcime, and quartz. ## Localities The most important and classic occurrence of reedmergnerite is the Green River Formation in Utah and Wyoming, USA, where it was discovered. It is also known from ultrabasic pegmatites in the Ilímaussaq complex in Greenland and from the Lovozero massif on the Kola Peninsula in Russia. These are the only confirmed, significant localities of this mineral worldwide.

Rarity

Very rare

For collectors

## Quality Criteria The most prized reedmergnerite specimens are those with well-formed, sharp, and transparent crystals, which is extremely rare. Rich crystalline aggregates clearly visible on the rock matrix are also highly valued. Association with other rare minerals from a given locality is key, increasing the scientific and collector's value of the specimen. Due to the small size of the crystals, even small but well-formed specimens are considered valuable. ## Popular Localities Specimens from the type locality – the Green River Formation in the USA – are by far the most sought after by collectors. Material from Russia (Kola Peninsula) and Greenland is extremely rare on the collector's market and is of interest to specialized institutions and systematic mineral collectors.

Care and storage

## Cleaning Reedmergnerite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, but prolonged soaking should be avoided. Always ensure the specimen is completely dry before storing it in the collection. ## What to Avoid Avoid contact with acids and strong chemicals, which can damage the mineral's surface. Reedmergnerite is sensitive to sudden temperature changes. It should not be exposed to prolonged direct sunlight, although its distinct effect on the mineral is not known. ## Storage Reedmergnerite specimens, especially those with well-formed crystals, should be stored in separate, padded collection boxes to protect them from mechanical damage and scratching by harder minerals. Due to its rarity, storage in stable room conditions is recommended.

External references

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