The shape of ekanite

Despite its high thorium content, and consequent radioactivity, ekanite is still commonly traded in the Sri Lankan gem market. Gem-quality ekanite is derived from several gravel deposits in the country. However, rough specimens do not show rounded shapes that would be expected for stones transported by water; rather, they have remarkably uneven surfaces with multitudes of hollows, bumps, and cavities. Only after the recent discovery of ekanite in its host calc-silicate rock near Ampegama, Southern Province, can the striking shapes be understood. Fluid-driven alteration of ekanite, still inside the host rock, results in the formation of banded nodules with heterogeneous disintegration rims of an earthy consistency. These rims are readily removed by weathering, whereas the interior remnant consisting of chemically and physically resistant, unaltered ekanite persists.