Category Silicate mineral Crystal system Tetragonal | Strunz classification 9.EA.10 Space group I422 | |
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Formula
(repeating unit) Ca2ThSi8O20 or (Ca,Fe,Pb)2(Th,U)Si8O20 Crystal class Trapezohedral (422)
H-M symbol: (4 2 2) | ||
Ekanite is an uncommon silicate mineral with chemical formula: Ca2ThSi8O20 or (Ca,Fe,Pb)2(Th,U)Si8O20. It is a member of the steacyite group. It is among the 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 are rare as the radioactivity tends to degrade the crystal matrix over time in a process known as metamictization.
The type locality is Ehiliyagoda, Ratnapura District, Sabaragamuwa Province, Sri Lanka, where it was first described in 1955 by F. L. D. Ekanayake, and it is named after him.
In Sri Lanka the mineral specimens occur as detrital pebbles. In the Tombstone Mountains of Yukon, Canada, the mineral is found in a syenitic glacial erratic boulder. In the Alban Hills of Italy it is found in volcanic ejecta.
