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Paraiba Tourmaline

Last updated: April 2026

Paraiba tourmaline (elbaite) derives its neon blue-green to blue color from copper and manganese. Found in Paraíba, Brazil; Mozambique; and Nigeria — all localities accepted as 'Paraiba' if Cu-bearing. Cu content requires laboratory analysis (EDXRF or ICP-MS); standard gemological instruments cannot confirm it. Heat treatment to remove brownish Mn absorption is widely accepted.

Paraiba Tourmaline has a specific gravity of 3.06 and a refractive index of 1.624–1.644, with a Mohs hardness of 7.0–7.5. It is uniaxial −.

Physical & Optical Properties

RI Range1.624–1.644
SG Range3.02–3.10
SG Typical3.06
Hardness (Mohs)7–7.5
Crystal SystemTrigonal
Optic CharacterDR Uniaxial (−)
Birefringence0.018
Dispersion0.017
Fluorescence LWInert
Fluorescence SWInert
Chelsea FilterGreen
PleochroismStrong Dichroic
ColorsBlue Violet, Green
SpeciesTourmaline
VarietyParaiba
Blue VioletGreen

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

Paraiba Tourmaline reads 1.625 – 1.643 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, 0.018 apart at their widest separation. MEANSThat gap IS the birefringence. Take max minus min across thewhole rotation — a single position understates it, so onereading is an incomplete one. 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

Paraiba Tourmaline Blinks 4× per turn (DR) 0° 45° 90° 135° ROTATION BETWEEN CROSSED POLARS Paraiba Tourmaline 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

Paraiba Tourmaline SG 3.02–3.10 WHERE IT SITS, AND WHAT ELSE IS THERE 1.0 2.0 3.0 4.0 5.0 SPECIFIC GRAVITY 9 other species in the table overlap this range, so a reading here narrows the field to 10 rather than naming the stone. Combine it with a refractive index to separate what is left. 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

Paraiba Tourmaline Two colours (dichroic) BEST ORIENTATION ROTATED 45° — THE NULL At its best orientation Paraiba Tourmaline shows dark blue-green in one window and light blue 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.

Chrome TourmalineGreen TourmalineIndicoliteRubelliteTourmalineWatermelon Tourmaline

Key Differentiators

Common Simulants

Commonly Confused With

Commonly confused with: Aquamarine, Glass.

Treatments

Related Comparisons

Paraiba Tourmaline Vs Apatite

Measurement Guides

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

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

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Studying for the GIA, FGA, or FEEG practical? Paraiba Tourmaline 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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