Ludlamite Value, Price, and Jewelry Information

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LUDLAMITE: Idaho (~0.5). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Ludlamite has a lovely green color but is too soft for wear. Large crystals are known from only a few localities, and cut stones are extremely rare.

Ludlamite Information

Data Value
Name Ludlamite
Formula Fe3(PO4)2 · 4H2O
Colors Apple green, dark green, pale green, greenish white, colorless.
Fracture Conchoidal
Hardness 3.5
Cleavage Perfect 1 direction
Crystallography Monoclinic. Crystals tabular, wedge-shaped; also granular.
Refractive Index 1.650-1.697
Birefringence 0.038-0.044
Luminescence None
Luminescence Present No
Absorption Spectrum Not diagnostic
Pleochroism None
Optics a = 1.650-1.653; β = 1.667-1.675; γ = 1.688-1.697. Biaxial (+), 2V= 82°.
Optic Sign Biaxial +
Luster Vitreous
Specific Gravity 3.19
Transparency Translucent to transparent
Etymology After Henry Ludlam, English mineralogist and collector.
Occurrence A secondary mineral in the oxidized zone of ore deposits; also due to the alteration of primary phosphates in granite pegmatites.




New Hampshire.

Cornwall, England; Hagendorf, Germany.

Blackbird Mine, Lemhi County, Idaho: fine crystals up to ½ inch across.

South Dakota: crystalline masses to 12 inches in diameter with 7 mm crystals at Keystone.




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