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Amazonite

Last updated: April 2026

Blue-green microcline feldspar colored by lead and water; frequently sold as a turquoise alternative. Under magnification, whitish cross-hatch or grid twinning (perthitic albite intergrowth) is visible in most specimens and is a key field indicator. Distinguished from turquoise by lower RI and SG; from chrysoprase by higher RI; from jade by lower RI/SG and cleavage. No pleochroic colour pair is recorded: O’Donoghue (Gems, 6th ed., 2006, via gemdat) gives microcline’s pleochroism as weak and names no colours, and the same reference has the material translucent to opaque and only rarely transparent — pleochroism is differential absorption of transmitted light, so there is usually nothing to read.

Amazonite has a specific gravity of 2.56 and a refractive index of 1.514–1.530, with a Mohs hardness of 6.0–6.5. It is biaxial −.

Physical & Optical Properties

RI Range1.514–1.530

SG Range2.54–2.58

SG Typical2.56

Hardness (Mohs)6–6.5

Crystal SystemTriclinic

Optic CharacterDR Biaxial (−)

Birefringence0.008

Dispersion0.012

Fluorescence LWInert

Fluorescence SWInert

Chelsea FilterInert

PleochroismWeak

ColorsGreen, Blue Violet

SpeciesFeldspar

VarietyMicrocline

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

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

Key Differentiators

Whitish cross-hatch twinning (perthitic grid) visible under magnification — diagnostic
Low RI (1.514–1.530) separates from turquoise (RI 1.61–1.65) and jade
Feldspar SG (~2.56) — lower than turquoise (~2.60–2.85)

Common Simulants

Turquoise: Turquoise: RI 1.61–1.65; SG 2.60–2.85. Much higher RI and SG than amazonite. Matrix pattern differs; no cross-hatch twinning.
Chrysoprase (chalcedony): Chrysoprase: RI ~1.535; SG ~2.58–2.64; microcrystalline aggregate; no twinning pattern. Usually more translucent than amazonite.
Jadeite: Jadeite: RI 1.654–1.688; SG 3.24–3.43. Much higher RI and SG. Interlocking granular texture, not perthitic twinning.

Commonly Confused With

Commonly confused with: Turquoise, Jadeite, Nephrite.

Treatments

Waxing / impregnation — surface stabilization

Measurement Guides

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

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