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Rhodonite

Last updated: April 2026

A manganese silicate known for its rosy pink color, often with black dendritic inclusions.

Rhodonite has a specific gravity of 3.60 and a refractive index of 1.716–1.752, with a Mohs hardness of 5.5–6.5. It is biaxial +.

Physical & Optical Properties

RI Range1.716–1.752
SG Range3.57–3.76
SG Typical3.60
Hardness (Mohs)5.5–6.5
Crystal SystemTriclinic
Optic CharacterDR Biaxial (+)
Birefringence0.014
Dispersion0.016
Fluorescence LWInert
Fluorescence SWInert
Chelsea FilterInert
PleochroismWeak
ColorsRed Pink, Brown, Black
SpeciesRhodonite
Red PinkBrownBlack

Measured with a polariscope, a refractometer, a hydrostatic balance, a Chelsea filter, a UV torch, a loupe, a darkfield loupe and a spectroscope — step-by-step for each.

Through the refractometer

Rhodonite varies 1.716 – 1.752 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 REFRACTIVE INDEX DORotate the stone through a full 360°, reading both edges atevery 45°. SEETwo boundaries, 0.014 apart at their widest separation. Thepair drawn here is one specimen: this species is publishedat 1.716 – 1.752, and the two edges slide together anywhereacross it, between the dashed marks. MEANSThat gap IS the birefringence — and it is the stable part.Where the pair sits varies by 2 printed divisions from stoneto stone, so the gap identifies and the position onlynarrows. Take max minus min across the whole rotation; asingle position understates it. Computed from gems.json — edge positions are arithmetic, not drawn. RI increases upward; the field above the boundary is the dark one.

Drawn from the refractive index above, on a 1.40–1.81 scale. How to take this reading.

Key Differentiators

Common Simulants

Commonly Confused With

Commonly confused with: Rhodochrosite.

Treatments

Measurement Guides

How to Identify a GemstoneHow to Measure Specific GravityHow to Use a RefractometerUV Fluorescence Testing

Identifying a rhodonite? Loupewise walks through these tests in order — RI, SG, fluorescence, and more.

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Studying for the GIA, FGA, or FEEG practical? Rhodonite is one of the 132 species in Loupewise’s drill and exam pool — practice identifying it from its measured properties under timed exam conditions.

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