Ludlamite Value, Price, and Jewelry Information

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

Ludlamite

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
Stone Sizes Ludlamite is seldom cut, and transparent material is always small. The potential may exist for 5-10 carat gems, but most are in the 1-2 carat or smaller range.
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, wedgeshaped; also granular.
Refractive Index 1.650-1.697
Birefringence 0.038-0.044.
Luminescence None.
Luminescence Present No
Absorption Spectrum Not diagnostic.
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.

Streak: Pale greenish white.

Optics: a = 1.650-1.653; β= 1.667-1.6 75; γ= 1.688-1.697.

Biaxial (+), 2V= 82°.

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.

Comments: 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.

Name: After Henry Ludlam, of London, English mineralogist and collector.

 

by Joel E. Arem, Ph.D., FGA