gemmology.dev – Utah Red Beryl: Wah Wah Mountains

Introduction

Red beryl, commercially known as "bixbite" (though the trade name creates
confusion with the manganese oxide mineral bixbyite), is arguably the rarest
gem-quality beryl variety. Commercial production is restricted to a single location:
the Wah Wah Mountains of Beaver County, Utah, where the Violet Claims mine operates
in Eocene topaz rhyolite of approximately 19–20 Ma age, formed during Basin and
Range extensional tectonics. ^[1]

Diagnostic significance rests on chromophore and geological host. Mn³⁺ substituting
Al³⁺ absorbs strongly across 490–560 nm, transmitting red; entirely different from
the Cr³⁺ of ruby or emerald. ^[1] The volcanic rhyolitic
host is distinctive; almost all other gem beryl forms in pegmatites. Deposit-specific
inclusions (small black bixbyite cuboids, topaz crystals from the same host, growth
tubes parallel to the c-axis) confirm provenance.

Crystal size is extremely limited (typically under 0.5 ct; above 3 ct exceptional).
Combined with geographic uniqueness, red beryl is sometimes cited as 1,000 times rarer
than emerald by weight mined.

Geological Setting

Wah Wah Mountains red beryl geology:

Host rock: Topaz rhyolite (a silica-rich, F-bearing volcanic flow) of
Eocene age (~20–19 Ma), formed during Basin and Range extensional tectonics
Formation mechanism: Beryl crystallises from an F-rich hydrothermal/vapour
phase generated during cooling of the rhyolitic magma; this vapour phase
penetrates vugs and fractures in the volcanic rock
Uniqueness: This is one of very few documented cases of gem beryl forming
in a purely volcanic (rhyolitic) setting rather than the usual pegmatitic or
contact-metamorphic environment
Additional observations on crystal morphology documented by later Journal of
Gemmology work

Colour and Chromophore

Red beryl colour origin:

Colour: Raspberry red to pink-red, purplish-red; the colour range is
consistent but saturation varies
Chromophore: Mn³⁺ substituting Al³⁺ in the beryl structure
Mn³⁺ absorption band in the ~490–560 nm region gives the red colour by
absorbing blue-green light, the complement of red ^[1]
This is fundamentally different from the Cr³⁺ colouring of ruby or emerald

Properties

Property	Value
Formula	Be₃Al₂Si₆O₁₈ (beryl), Mn³⁺ colouring
Crystal system	Hexagonal; uniaxial negative
RI	1.564–1.584 (ne); 1.568–1.590 (no); DR ~0.006
SG	2.66–2.70
Hardness	7.5–8 (Mohs)
Crystal habit	Tabular to short hexagonal prisms; very small
Typical size	≤2 ct cut; usually <0.5 ct; >1 ct exceptional
Fluorescence	Generally inert

Inclusions

Inclusions found in Utah red beryl:

Two-phase inclusions: Liquid + gas
Growth tubes: Parallel to the c-axis
Topaz crystals: From the same rhyolitic host; geologically associated
Bixbyite crystals: Iron-manganese oxide; small black cuboids
Hematite: Iron oxide
Needle-like inclusions: Occasionally present

Distinguishing Red Beryl

Key separations from simulants and similar gems:

From Red Spinel

Red spinel is isotropic (cubic); red beryl is uniaxial negative (hexagonal)
On polariscope: spinel SR, red beryl DR
SG differs: spinel ~3.60; red beryl ~2.67 (a major difference)
RI differs: spinel 1.712–1.736; red beryl 1.564–1.590

From Rubellite (Red Tourmaline)

Both are DR (doubly refractive) and red
SG: rubellite ~3.02; red beryl ~2.67
RI: rubellite ~1.614–1.679; red beryl ~1.564–1.590 (lower)
Birefringence: rubellite 0.014–0.021; red beryl ~0.006 (lower)
Pleochroism: rubellite dichroic (deep pink / pale pink); red beryl
pleochroism less dramatic for red material

From Red Glass

Glass is isotropic; red beryl is doubly refractive: polariscope separation
SG of glass varies but usually 2.3–4.5; red beryl SG is characteristic
Chelsea filter and spectrum may help confirm beryl species

Utah Red Beryl: Wah Wah Mountains