Reedmergnerite
Sodium boron silicate (NaBSi3O8)
A rare boron-bearing feldspar, the boron analogue of albite, first found in oil-shale nodules of the Green River Formation.
- Mohs hardness
- 6.5-7
- Color
- Colorless to white, sometimes pale gray
- Type
- mineral
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Overview
Reedmergnerite is a rare feldspar-group mineral that is the boron analogue of albite: it has the same structure but with boron replacing aluminum, giving the composition NaBSi3O8. It crystallizes in the triclinic system, like albite, and is typically colorless to white.
It was first discovered in the Eocene oil shales of the Green River Formation in Utah, occurring as tiny crystals within carbonate nodules. The mineral is named after Frank Reed and John Mergner, technicians at the U.S. Geological Survey.
Reedmergnerite is significant mineralogically because boron rarely substitutes for aluminum in tetrahedral framework silicates, making it an unusual member of the feldspar family found only in special boron- and sodium-rich settings.
Formation & geology
Reedmergnerite forms in boron-rich, sodium-rich chemical sedimentary and alkaline environments. In its Green River type locality it crystallized authigenically (in place) within carbonate-rich nodules of an ancient alkaline lake deposit, where boron-enriched pore fluids reacted with silica and sodium.
It also occurs in unusual alkaline igneous and hydrothermal rocks, most famously at the Dara-i-Pioz massif in Tajikistan, a locality renowned for exotic boron and alkali minerals, where larger crystals are found. Such boron-rich, peralkaline settings are required for its rare formation.
How to identify it
Reedmergnerite is colorless to white with a vitreous luster, hardness 6.5-7 (slightly harder than typical feldspars), white streak, and feldspar-like cleavage. Crystals from sedimentary rocks are very small, while Tajik material can be coarser.
It is visually almost indistinguishable from albite and other colorless feldspars and requires chemical or X-ray analysis to confirm the boron content. Its occurrence in boron-rich oil shales or in exotic alkaline rocks like Dara-i-Pioz is the strongest contextual clue.
Uses & significance
Reedmergnerite has no commercial, industrial, or gem use owing to its extreme rarity. Its importance is purely scientific and to mineral collectors, who value it as a rare boron feldspar and a curiosity of unusual crystal chemistry.
Study of reedmergnerite helps mineralogists understand how boron can substitute into framework silicate structures and illuminates the geochemistry of boron in alkaline lakes and peralkaline igneous systems. Fine crystals from Dara-i-Pioz are prized specimens among collectors of rare species.
Frequently asked questions
What is reedmergnerite?
It is a rare feldspar-group mineral, the boron analogue of albite, with the composition NaBSi3O8, in which boron replaces aluminum.
Where was reedmergnerite first found?
In carbonate nodules within the oil shales of the Green River Formation in Utah, USA.
Is reedmergnerite used for anything?
No. It is too rare for any practical use and is of interest only to scientists and mineral collectors.
Where can good reedmergnerite crystals be found?
The Dara-i-Pioz alkaline massif in Tajikistan is famous for producing larger, well-formed reedmergnerite crystals.
Reedmergnerite guides
In-depth guides for identifying, valuing, and understanding Reedmergnerite.
