Ekanite

Chemical formula: Ca₂Th⁴⁺Si₈O₂₀

Ekanite is a rare, naturally radioactive silicate mineral, valued by collectors for its green color and metamictization phenomenon.

## Characteristics Ekanite is a complex calcium and thorium silicate, known for its natural, often strong radioactivity. It typically occurs as rounded, glass-like fragments, originally found in river sediments. Its crystal structure is often destroyed by its own radiation (metamictization), giving it an appearance similar to obsidian or other natural glass. It rarely forms well-developed crystals, which have a tabular or prismatic habit. ## Physical Properties Ekanite is characterized by a vitreous luster. Its hardness is variable and depends on the degree of metamictization – specimens with preserved crystal structure achieve a hardness of about 6.5 on the Mohs scale, while completely metamict forms have a hardness in the range of 4.5-5. The mineral's density is approximately 3.28 g/cm³. It is brittle and has an uneven or conchoidal fracture. ## Colors and Varieties This mineral most often takes on colors ranging from green, through yellowish-green, dark green, to brown. Some specimens can be almost black. Starry varieties (exhibiting asterism) when cut into a cabochon are rare. No formal commercial or color varieties are distinguished. ## History and Name Ekanite was discovered in 1953 in Sri Lanka by F. L. D. Ekanayaka, after whom the mineral is named. Initially, due to its appearance and metamict state, it was considered a natural glass. Only later research confirmed it to be a new mineral species. It was formally described and recognized by the IMA in 1961. ## Uses Due to its rarity and radioactivity, ekanite has no industrial applications. However, it is a sought-after and valued collector's stone. It is sometimes cut (usually into cabochons or faceted stones) for advanced gemological collectors, but its processing and possession require specialized knowledge and precautions.

Properties

Mohs hardness: 4.5
Color: Green in various shades, straw-yellow, dark red, colourless
Luster: Vitreous
Streak: White
Density: 2.95
Cleavage: Distinct on {101}, indistinct on {001}
Fracture: Irregular/Uneven
Transparency: Transparent to translucent
Crystal system: Tetragonal

Diagnostic features

## Identification The most important diagnostic feature of ekanite is its strong radioactivity, easily detectable with a Geiger counter. Visually, it often resembles green or brown glass. In crystalline form, it exhibits tetragonal symmetry. The green color combined with high radioactivity is almost unambiguous for this mineral. ## Distinguishing from Similar Minerals Ekanite can be confused with other green, metamict minerals containing thorium or uranium, such as thorite or zircon. Differentiation requires specialized tests, but ekanite's very strong radioactivity is a good indicator. It can also be confused with obsidian or moldavite, but these are not radioactive. ## Crystal Forms Well-formed crystals are extremely rare. If they occur, they take the form of tetragonal, tabular or short-prismatic crystals. Most often, it is found as irregular, rounded pebbles and fragments in alluvial deposits (riverbed gemstones).

Geological environment

## Genesis Ekanite is a mineral of metamorphic or magmatic origin. It forms in skarns, syenites, and associated pegmatites. Primary deposits are found in rocks rich in calcium, silica, and thorium. Most specimens, especially from Sri Lanka, come from secondary (alluvial) deposits, where the mineral has accumulated in river sediments after the weathering of the parent rock. ## Mineral Associations Associated minerals in parent rocks (syenites) include diopside, scapolite, titanite, apatite, and fluorite. In alluvial deposits, it occurs together with other heavy and resistant minerals, such as zircon, corundum (sapphire, ruby), and spinel. ## Localities The most important and historical occurrence of ekanite is Sri Lanka, especially in the Ratnapura region, where it is found in river sediments. Other significant localities include Mont-Saint-Hilaire in Quebec (Canada), where well-formed crystals have been found, and the Sayan Mountains in eastern Siberia (Russia).

Rarity

Very rare

For collectors

## Quality Criteria The most prized by collectors are specimens with an intense, emerald-green color and good transparency. Rare, well-formed crystals, especially from the Canadian locality of Mont-Saint-Hilaire, are exceptionally sought after. For specimens from Sri Lanka, size and quality of rounded pebbles are important. Specimens exhibiting asterism (star effect) when cut are a rarity. ## Popular Localities The most famous specimens, especially those of gemological quality, come from the river deposits of the Ratnapura district in Sri Lanka. In turn, specimens from the Poudrette quarry at Mont-Saint-Hilaire in Canada are considered the best in terms of crystallography.

Care and storage

## Cleaning Ekanite specimens should only be cleaned dry, using a soft brush or compressed air to remove dust. Avoid contact with water and any chemicals. ## What to Avoid Ekanite is highly radioactive due to its high thorium content. Prolonged, close contact with the mineral must be strictly avoided. It should not be worn directly on the body. Inhaling dust generated during any processing should be avoided. The mineral is brittle and sensitive to impacts and temperature changes. ## Storage Ekanite must be stored in compliance with radiological protection principles. It is recommended to keep it in a separate, lead or thick glass container, away from other minerals that could be damaged by radiation. The container should be clearly marked as radioactive material. It should be stored out of reach of children and individuals unaware of the hazard.