Reedmergnerite Identification Guide

What Reedmergnerite Looks Like

Reedmergnerite is a rare sodium boron silicate (NaBSi₃O₈), the boron analog of albite feldspar — boron substitutes for aluminum in the framework. It is typically colorless, white, or pale cream, with a vitreous luster and transparent to translucent appearance. Crystals are triclinic, occurring as small tabular-to-stubby grains, and it is most often found embedded in sedimentary or alkaline rocks rather than as showy specimens. This is a collector/micro-mineral species, not a common field find.

Step-by-Step Field ID Checklist

1. Establish the geologic context first. It occurs in boron-rich sedimentary rocks (oil-shale dolostones) and in alkaline/peralkaline igneous and pegmatitic settings — context narrows the field dramatically.
2. Look for feldspar-like habit. Blocky-to-tabular colorless grains with flat reflective faces.
3. Find cleavage surfaces. Two cleavage directions intersecting near 90° (feldspar-type).
4. Check hardness against quartz. Slightly softer than quartz.
5. Confirm by lab methods. Because it mimics albite closely, positive ID usually needs X-ray diffraction, optical (low refractive index), or chemical (boron) analysis.

Key Diagnostic Tests

• Mohs hardness: ~6–6.5; harder than calcite, slightly softer than quartz.
• Cleavage: Two good cleavages meeting at roughly 90° (feldspar group).
• Streak: White.
• Density: ~2.8 g/cm³ — slightly higher than albite (~2.62).
• Acid: Insoluble in dilute HCl (distinguishes from associated carbonates).
• Optics/chemistry: Low refractive indices; confirmatory test is detecting boron and the distinctive XRD pattern.

Common Look-Alikes and How to Tell Them Apart

• Albite (and other feldspars): Nearly identical visually and in hardness/cleavage. The reliable separation is chemistry (boron present) and slightly higher density, requiring XRD or microprobe analysis.
• Danburite (CaB₂Si₂O₈): Another borosilicate but harder (7–7.5), with orthorhombic prismatic crystals and poor cleavage; reedmergnerite is softer with feldspar cleavage.
• Quartz: Harder (7), no cleavage (conchoidal fracture), and shows hexagonal habit when crystallized.
• Datolite: Calcium borosilicate, harder and with a greasy luster and no good cleavage.

Where Reedmergnerite Is Found

The type locality is the Green River Formation oil shales of Utah, USA, where it occurs in boron-rich dolomitic beds. It is also known from alkaline/peralkaline complexes such as the Lovozero and Khibiny massifs (Kola Peninsula, Russia) and other agpaitic pegmatites. Because specimens are tiny and look like ordinary feldspar, locality data plus instrumental confirmation are essential.

Formation and Collecting Notes

Reedmergnerite is genuinely rare and chiefly of interest to systematic mineral collectors. It crystallized in two very different boron-rich settings: the dolomitic oil-shale beds of the Green River Formation, where it grew as small authigenic crystals in sediment, and agpaitic (peralkaline) igneous complexes and their pegmatites, where exotic sodium-rich fluids supplied the boron.

Because it is a near-perfect mimic of albite, treat any field identification as provisional until backed by instrumental data. Useful first-pass steps are to confirm feldspar-type cleavage and a hardness just under quartz, then check the associated minerals and rock type — a boron-rich dolostone or an alkaline syenite/pegmatite makes reedmergnerite plausible, whereas an ordinary granite almost certainly means plain albite. Photograph the matrix and record the locality precisely; reliable confirmation comes from a measured slightly elevated density (~2.8), low refractive indices, detection of boron, and the diagnostic X-ray diffraction pattern. Do not expect showy crystals — most specimens are millimeter-scale grains best appreciated under magnification.