|Crystal system||Orthorhombic/ Cubic|
|Color||Steel-gray to tin-white with a rose tint, brass yellow|
|Crystal habit||Acicular prismatic|
|Twinning||Stellate and cruciform twins common|
|Mohs scale hardness||6 - 6.5|
|Solubility||insoluble in water|
Orthorhombic ferroselite and its isometric polymorph dzharkenite are iron selenides of general formula FeSe2 precipitated under reducing conditions in anoxic environments. They are a source of selenium in the Rocky Mountains where selenium occurrence is associated with Upper Cretaceous shale deposits.
In the frame of safety assessment calculations made for deep disposal of high-level radioactive waste, ferroselite and dzharkenite are also considered in geochemical calculations as one of the mineral phases limiting the solubility of Selenium-79.
Dzharkenite's type locale is in the Suluchekinskoye Se-U deposit in the Dzharkenskaya Depression of the Middle Ili River, Almaty Province, in southeastern Kazakhstan. It was discovered in 1995 and named after the depression.
- Coccolithophorid, a group of marine planktonic unicellular algae fixing selenium in Upper Cretaceous chalk and shale formations
- Emiliania huxleyi, a major species of coccolithophorid active in selenium bioconcentration