Ludlamite

Big Photo

Blackbird Mine, Tenmile Mining District, Idaho County, Idaho, USA
0.52 carats
© Rarestone.com

Ludlamite was named after Henry Ludlam, a British collector of rare minerals. It was first discovered in 1876 in Wheal Jane mine in Cornwall, England.

Ludlamite is a rare phosphate mineral. It forms apple- to bright green prismatic crystals. Ludlamite is occasionally faceted, but the crystals are always small.

Ludlamite Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
General Information
Chemical Formula
(Fe
2+
 
,Mg,Mn
2+
 
)
 
3
(PO
 
4
)
 
2
 · 4H
 
2
O
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Physical Properties of Ludlamite
Mohs Hardness3 to 4
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Specific Gravity3.1 to 3.2
Walter Schumann, Gemstones of the world (2001)
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Cleavage QualityPerfect
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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FractureUneven
Arthur Thomas, Gemstones (2009)
Optical Properties of Ludlamite
Refractive Index1.653 to 1.693
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Optical CharacterBiaxial/+
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Birefringence0.040
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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PleochroismNil
Arthur Thomas, Gemstones (2009)
DispersionRelatively weak
Arthur Thomas, Gemstones (2009)
Colour
Colour (General)Light- to apple-green, colourless
Walter Schumann, Gemstones of the world (2001)
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TransparencyTransparent
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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LustreVitreous
Arthur Thomas, Gemstones (2009)
Crystallography of Ludlamite
Crystal SystemMonoclinic
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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HabitPrismatic
Michael O’Donoghue, Gems, Sixth Edition (2006)
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Geological Environment
Where found:Occurs in granite pegmatites, resulting from the alteration of primary phosphates
Michael O’Donoghue, Gems, Sixth Edition (2006)
Further Information
Mineral information:Ludlamite information at mindat.org
Significant Gem Localities
UK
 
  • England
    • Cornwall
USA
 
  • Idaho
    • Lemhi County
      • Blackbird Mining District
        • Blackbird mine complex
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 425
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