SAND-Stone, a genus of stones belonging to the order of saxa; and including all those which consist of such minute particles that they cannot easily be discerned by the eye. The species enumerated by Cronstedt are,

1. Those cemented by a clay, of which there are two varieties; one with porcelain clay, the other with common clay. The former is met with in Sweden under the stratum of coal in a coal-mine in the province of Bohne, and is very hard and refractory in the fire; the other is found in the island of Gothland.

2. With lime, resembling mortar made with coarse sand. There are two varieties, one consisting of transparent grey-coloured grains of quartz and white limestone, the other of a loose texture, hardening in the air; but having the particles too fine to be visible. The former of these is found in Sweden, the latter in France and Livonia.

3. Sand-stone having its particles bound together by an unknown cement. Of this there are four varieties;

1. Loose; 2. Somewhat hard; 3. Compact; 4. Very hard; all of them found in different parts of Sweden.

4. Cemented by rust of iron, found in the form of loose stones in several places.

Cronstedt informs us that the greatest part of sandstones consist of quartz and mica, being those substances which most readily admit of granulation without being reduced to powder. Some years ago the Baron de Dietrich showed a singular variety of sand-stone at Paris. It consists of small grains of hard quartz which strike fire with steel united with some micaceous particles. It is flexible and elastic, the flexibility depending on the micaceous part and softness of the gluten with which the particles are cemented. This elastic stone is said to have been found at Brazil, and brought to Germany by his excellency the marquis de Lavradio. There are also two tables of white marble, kept in the palace of Borghese at Rome, which have the same property. But the sparthy particles of their substance, though transparent, are rather soft, and may be easily separated by the nail. They effervesce with aquafortis, and Sandal, there is also a small mixture of minute particles of talk Sandarach, or mica.

Sand-stones are of great use in buildings which are required to resist air, water, and fire. Some of them are soft in the quarry, but become hard when exposed to the air. The loose ones are most useful, but the solid and hard ones crack in the fire, and take a polish when used as grindstones. Stones of this kind ought therefore to be nicely examined before they are employed for the usual purposes. Our author observes that the working masons, or stone-cutters, ought to wear a piece of frise or baize before their mouths, to preserve themselves from a consumption which their business is otherwise apt to bring on. Limestone, however, is not observed to have this effect.

To the list of sand-stones Fabroni adds gritstone, of greater or less hardness; mostly of a grey, and sometimes of a yellowish colour, composed of a filaceous and micaceous sand, but rarely of a sparry kind, with greater or lesser particles closely connected with an argillaceous cement. It strikes fire with steel, vitrifies in a strong fire, and is generally indissoluble in acids. It is used for mill-stones, wheel-stones, and sometimes for filtering stones, as well as for building.