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.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Crystallography||Monoclinic. Crystals tabular, wedgeshaped; also granular.|
|Colors||Apple green, dark green, pale green, greenish white, colorless.|
|Cleavage||Perfect 1 direction. Fracture conchoidal. Brittle.|
|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.|
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.
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.