The Collaborative International Dictionary
Itacolumite \It`a*col"u*mite\, n. [From Itacolumi, a mountain of Brazil.] (Min.) A laminated, granular, siliceous rocks, often occurring in regions where the diamond is found.
n. (context mineralogy English) A porous yellow sandstone that is flexible when cut into thin strips.
Itacolumite is a naturally occurring porous, yellow sandstone that is flexible when cut into thin strips. It occurs in great numbers at Itacolumi, in the southern portion of Minas Gerais, Brazil. It is also found in Jhajjar, India; Georgia; and Stokes and McDowell Counties North Carolina, USA. It is the best and most widely known example of a flexible sandstone and is a source of diamonds found in the Minas Gerais area.
On the split faces of the slabs, scales of greenish mica are visible, but in other respects the rock seems to be remarkably pure. If a piece which is a foot or two long and half an inch thick is supported at its ends it will gradually bend by its own weight. If it is then turned over it will straighten and bend in the opposite direction. Flakes a millimetre or two thick can be bent between the fingers and are said to give out a creaking sound, but specimens showing this property form only a small part of the whole mass of the rock.