grits, in natural history, a genus of fossils, found in minute masses, forming together a kind of powder, the several particles of which are of no determinate shape, nor have any tendency to the figure of crystal, but seem rudely broken fragments of larger masses; not to be dissolved or diluted by water, but retaining their figure in it, and not cohering by means of it into a mass; considerably opake, and in many species fermenting with acids: often fouled with heterogeneous matters, and not unfrequently taken in the coarser flinty and mineral or metallic particles.

Grits are of various colours, as, 1. The flinty and sparly grits, of a bright or greyish white colour. 2. The red flinty grits. 3. The green flinty grits, composed of homogenes sparly-particles. 4. The yellow grit, of which there is only one species, 5. The black and blackish grits, composed of flinty or talc particles.