Formula: Ca2Y2(SiO3)4(CO3).H2O
Cyclosilicate (ring silicate)
Specific gravity: 3.52
Hardness: 5 to 6
Streak: White
Colour: Chestnut brown, straw yellow, colourless
Solubility: Effervesces slowly in cold dilute hydrochloric acid
Common impurities: Na

Igneous environments

Kainosite occurs in vugs in pegmatites in granite and alkaline complexes (HOM). It may form from yttrialite-(Y) and pseudomorphs of kainosite after yttrialite(Y) have been found (Dana).


At the Bancroft area, Ontario, Canada, some of the finest specimens of kainosite-(Y) have been found, associated with chamosite, pyrite, quartz, calcite, sphalerite, fluorite, uraninite, zircon and molybdenite (HOM, R&M 94.5.413-414).

At the Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Quebec, Canada, kainosite-(Y) occurs in cavities in breccia (Dana).

At Baveno, Verbano-Cusio-Ossola Province, Piedmont, Italy, kainosite-(Y) occurs in granite (Dana).

At Mount Malosa, Zomba, Southern Region, Malawi, a few crystals of kainosite-(Y) to 4 cm have been found on a matrix of feldspar and aegirine (Min Rec 35.3.255).

The type locality is the Igletjødn Feldspar Quarry, Hæstad, Hidra, Flekkefjord, Agder, Norway.

At the Nordmark District, Filipstad, Värmland County, Sweden, yellow-brown to chestnut-brown kainosite-(Y) occurs in an iron mine associated with diopside, clinochlore, magnetite and apatite (Dana, HOM).

At the Porthill Mining District, Boundary county, Idaho, USA, colourless to white kainosite-(Y) has been discovered in a thorite vein. Kainosite-(Y) is one of a small group of minerals in which yttrium is a major constituent. The thorite vein in which it occurs is intruded into a diorite sill and is made up chiefly of quartz and thorite. Other minerals include calcite, chlorite, magnetite, allanite, apatite and kainosite. Kainosite was found only in the vein material having the highest radioactivity. It is commonly either adjacent to or intergrown with allanite, although in places it is intergrown with calcite (AM 49.1636-1741, as cenosite).

At the Grenci-Ellis Granite quarry, Mount Desert, Hancock county, Maine, USA, kainosite-(Y) occurs in a granite pegmatite with kamphaugite-(Y) (Dana).

At Rossie, St. Lawrence county, New York, USA, kainosite-(Y) occurs in galena mines, with calcite (Dana).

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