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Category Silicate mineral
(repeating unit)
Ca2ThSi8O20 or (Ca,Fe,Pb)2(Th,U)Si8O20
Color Green, yellow, dark red
Crystal habit Pyramidal crystals, granular to massive
Crystal system Tetragonal
Cleavage Distinct on {101}
Fracture Brittle, uneven
Mohs scale hardness 4.5
Luster Vitreous
Streak White
Diaphaneity Transparent to translucent
Specific gravity 2.95 - 3.28
Optical properties Uniaxial (-) 2V = 10 - 15°
Refractive index nω = 1.580 nε = 1.568
Birefringence δ = 0.012
Other characteristics Radioactive, metamict
References [1][2][3]

Ekanite is an uncommon mineral notable primarily as being among the very few gemstones that are naturally radioactive. Most ekanite is mined in Sri Lanka, although deposits also occur in Russia and North America. Clear and well-colored stones command the best prices, but such stones are rare; the mineral's radioactivity tends to degrade the crystal matrix over time in a process known as metamictization.

Ekanite was first described in 1955 by F. L. D. Ekanayake.[4][5] The mineral is named for Mr. F. L. D. Ekanavake.[6]


  1. ^ http://www.mindat.org/min-1361.html Mindat
  2. ^ http://rruff.geo.arizona.edu/doclib/hom/ekanite.pdf Handbook of Mineralogy
  3. ^ Ekanite Mineral Data at Webmineral
  4. ^ New Minerals, American Mineralogist
  5. ^ B. W. Andeson, G. F. Claringbull, R. J. Davis, and D. K. Hill (1961). "Ekanite, a new metamict mineral from Ceylon". Nature 190 (4780): 997. Bibcode:1961Natur.190..997A. doi:10.1038/190997a0. 
  6. ^ New Minerals, American Mineralogist