Willemite

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Physical & Optical Properties

Mohs Hardness 5.5
Specific Gravity 3.89 – 4.18
Refractive Index 1.687 – 1.723
Crystal System Trigonal
Luster Resinous
Cleavage Distinct
Fracture Sub-Conchoidal
Color various
Birefringence 0.028
Pleochroism Nil

Mohs Hardness

Mohs Hardness: 5.5
1 Soft10 Hard

Crystal System

a a a Trigonal (Rhombohedral) a = b = c, α = β = γ ≠ 90°

Value & Market

Price Tier Budget (< $50/ct)

About Willemite

Willemite is a zinc silicate mineral renowned for its extraordinarily bright green to yellow fluorescence under ultraviolet light, one of the most dramatic fluorescence effects of any mineral in the world. It forms in the oxidized zone of zinc ore deposits and in metamorphic limestone skarns, with the Franklin and Sterling Hill mines of New Jersey, USA producing the world's most spectacular fluorescent willemite specimens. Transparent gemstone-quality crystals of yellow-green to brown willemite are occasionally faceted as collector pieces.

Jewelry Use

Durability 4/10

Science FYI Family

Frequently Asked Questions

What is Willemite?
Willemite is a zinc silicate mineral renowned for its extraordinarily bright green to yellow fluorescence under ultraviolet light, one of the most dramatic fluorescence effects of any mineral in the world. It forms in the oxidized zone of zinc ore deposits and in metamorphic limestone skarns, with t
What is the hardness of Willemite?
Willemite has a Mohs hardness of 5.5, making it moderate for use in jewelry.
What color is Willemite?
Willemite is primarily Various.
How much does Willemite cost?
Willemite falls into the Budget (< $50/ct) price range. Prices vary based on color, clarity, cut, and origin.
What is the crystal system of Willemite?
Willemite belongs to the Trigonal crystal system.

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