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stone, grit-stone and argillaceous

GIZIT-STONE, a stone consisting of particles of sand agglutinated together. Of this kind of stone there are many varieties, diffi•ring in the size of the particles of sand t hat compose them, the several properties of these sands, and their various degrees of compactness and agglutination.

Some of them are used for building, others for grinding, others for whetting sharp steel instruments, and others for filtering water. See STONE, and WHETSTONE.

Gaur-SroxE. in mining, a hard granular or gritty stone, composed of grains of silex or quartz, cemented together, generally either by a silicions, an argillaceous, or a ferru ginous cement. The first of these, or the silicious grit-stones, are alone fit to be used in repairing roads. The other sorts, in wet weather, soon become a hehvy sandy mire upon the road ; when the argillaceous parts are dissolved and washed away by the winter rains, this mire changes in summer to loose sand, rendering the roads almost intolerable. Most tra vellers will have observed this in the argillaceous grit-stone district about Ashby de la Zouch, in and numerous other coal countries. and the ferruginous grit-stone district about Woburn. in Bedtbrdshire, and other places.

The greater part of the numerous grit-stone rocks and beds of such stone in the coal-mines, are argillaceous, of a fine grit, with minute plates of mica, and are unfit for roads, until hardened by the action of fire ; still, however, very weak and improper materials for rozufmaking, if better can be produced.

A large portion of the argillaceous grit-stones have but a slight disposition to perish or moulder when exposed, and can slight used in walls and ordinary buildings ; others will perish in a few years; and a large portion of what appears, when first dug, at proper distances below the surface, to be very hard grit-stone, will, after a very short time of expo sure, fall to a loamy or clayey sand ; such very perishable grit-stone strata are called, by the colliers, stone-binds, gray. beds, &e., except about Newcastle, where they are denomi nated sand-stones.

In some places, crystallized granular lime-stones occur, as in the yellow or magnesian lime-stone range, near Mansfield in Nottinghamshire, and such are sometimes, though impro perly, called yrit-stones, or gritty lime-stones. See