It is readily fissile, like slate, but powerfully resists the cross fracture, which is conchoidal.
I noticed some conchoidal hollows more than a foot in diameter.
Hornstone is more brittle than flint and has a splintery rather than a conchoidal fracture.
It has a conchoidal fracture, and is without smell or taste.
It is of black colour; its fracture is conchoidal, and it has a lustrous surface.
Their fracture is conchoidal, with hmatitic (iron-ore pimpled) surface.
There is an imperfect cleavage parallel to the basal pinacoid, and the fracture is conchoidal.
When of good quality it is too hard to be scratched by the nail, has a conchoidal fracture, and a sp.
The paste is very fine 327 grained, and breaks with a conchoidal fracture.
In colour they vary from ash-grey to black, and their fracture is conchoidal.