Charoite (/tʃæroʊ.aɪt/ CHAR-ow-ait) is a rare silicate mineral with the chemical composition K(Ca,Na)2Si4O10(OH,F)•H2O, first described in 1978.

It has an unusual swirling, fibrous appearance, sometimes chatoyant, and that, along with its intense color, can lead many to believe at first that it is synthetic or enhanced artificially.

[5] Charoite consists of oxygen (43.75%), silicon (27.65%) and calcium (17.53%) mainly, but its composition includes potassium (10.69%) - which gives it its radioactive properties - and hydrogen (0.39%) as well.

It has a barely detectable, 0.65% radioactivity concentration per Gamma Ray American Petroleum Institute Units.

It is found where a syenite of the Murun Massif has intruded into and altered limestone deposits producing a potassium feldspar metasomatite,[5] and forms between 200 - 250 °C.