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Rhodochrosite

Last updated: April 2026

Manganese carbonate with intense rose-red to pink color and extreme birefringence. Best known in massive stalactitic form from Argentina ('Inca Rose') with concentric white/pink banding, but transparent faceted crystals also occur.

Rhodochrosite has a specific gravity of 3.50 and a refractive index of 1.600–1.820, with a Mohs hardness of 3.5–4.0. It is uniaxial −.

Physical & Optical Properties

RI Range1.600–1.820
SG Range3.40–3.70
SG Typical3.50
Hardness (Mohs)3.5–4
Crystal SystemTrigonal
Optic CharacterDR Uniaxial (−)
Birefringence0.220
Dispersion0.015
Fluorescence LWWeak orange
Fluorescence SWInert
Chelsea FilterInert
PleochroismWeak
ColorsRed Pink
SpeciesRhodochrosite
Red Pink

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

Rhodochrosite reads 1.600 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.820 REFRACTIVE INDEX DORotate the stone through a full 360°, reading at every 45°. SEEOne boundary, at 1.600. However far you rotate, a second onenever appears. MEANSA trap, and here is how to escape it. This stone IS doublyrefractive, but its upper edge sits at 1.820 — past the 1.81ceiling — so the instrument cannot show it. One edgetherefore does NOT prove singly refractive. Move to a secondfacet and read again: if a single edge still holdsabsolutely still on both, that is your answer, and ifanything moves it never was singly refractive. 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.

Through the polariscope

Rhodochrosite Blinks 4× per turn (DR) 0° 45° 90° 135° ROTATION BETWEEN CROSSED POLARS Rhodochrosite blinks light-dark four times in a full turn. That is doubly refractive. It does NOT tell you uniaxial from biaxial — that is the optic figure, which needs a conoscope. Computed from optic character and transparency in gems.json. A polariscope separates singly refractive, doubly refractive and aggregate — it does not show the optic sign.

Drawn from the optic character and transparency above. A polariscope separates singly refractive, doubly refractive and aggregate; the optic sign needs a conoscope. How to take this reading.

Specific gravity, and what it rules out

Rhodochrosite SG 3.40–3.70 WHERE IT SITS, AND WHAT ELSE IS THERE 1.0 2.0 3.0 4.0 5.0 SPECIFIC GRAVITY 28 other species in the table overlap this range, so a reading here narrows the field to 29 rather than naming the stone. This is the crowded part of the scale — the same careful measurement is worth far more higher up. Computed from the specific-gravity range in gems.json. Hydrostatic weighing — the bench method this site recommends; heavy liquids are toxic and regulated. Faint ticks are the other species in the table.

Drawn from the specific-gravity range above, against every other species in the table. How to take this reading.

Through the dichroscope

Rhodochrosite Two colours (dichroic) BEST ORIENTATION ROTATED 45° — THE NULL At its best orientation Rhodochrosite shows pink in one window and pale pink in the other. Rotate the instrument 45° and the two windows become IDENTICAL — the null. So "both windows the same" means either the stone is singly refractive or you are holding the instrument at the wrong angle, and the only way to tell is to turn it. Computed from pleochroism and pleochroic colours in gems.json. Window tints are derived mechanically from the colour words, not chosen; a neutral pair depicts no colour at all.

Drawn from the pleochroism above. Two windows that match mean either no pleochroism or the wrong angle — turn the instrument to tell. How the dichroscope compares.

Key Differentiators

Common Simulants

Commonly Confused With

Commonly confused with: Rhodonite, Rose Quartz.

Treatments

Measurement Guides

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

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

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Studying for the GIA, FGA, or FEEG practical? Rhodochrosite 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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