Hard, but yields to the file, and easily broken. Sp. gr. 3.25. It froths like zeolite before the blow-pipe, melting into a black enamel, or a dark green glass. According to Vauquelin's analysis, it contains 44 silica, 18 alumina, 19 lime, 14 oxide of iron, and 4 oxide of manganese. It is found in beds at Thum in Saxony; in Killas at Botallack near the Land's-end, Cornwall; and at Trewellard in that neighbourhood.*

AZOTE. See GAS (NITROGEN).

* AZURE-STONE, OF LAPIS LAZULI. This massive mineral is of a fine azure blue colour. Lustre glistening. Fine grained uneven fracture. Scratches glass, but scarcely strikes fire with steel. Opaque, or translucent on the very edges. Easily broken. Sp. grav. 2.85. In a very strong heat it intumesces, and melts into a yellowish-black mass. After calcination it forms a jelly with acids. It consists of 46 silica, 28 lime, 14.5 alumina, 3 oxide of iron, 6.5 sulphate of lime, and 2. water, according to Klaproth. But by a later and most interesting research of MM. Clement and Desormes, lapis lazuli appears to be composed of 34 silica, 33 alumina, 3 sulphur, and 22 soda. (Ann. de Chimie, tom. 57.) In this analysis, however, a loss of eight per cent was experienced. These distinguished chemists consider the above ingredients essential, and the 2.4 of lime and 1.5 of iron, which they have occasionally met with, as accidental. It is from azure-stone that the beautiful and un

changeable blue colour ultramarine is pre pared. The finest specimens are brought from China, Persia, and Great Bucharia. They are made red-hot in the fire, and thrown into water to render them easily pulverizable. They are then reduced to a fine powder, and intimately combined with a varnish, formed of rosin, wax, and boiled linseed oil. This pasty mixture is put into a linen cloth, and repeatedly kneaded with hot water: the first water, which is usually dirty, is thrown away; the second gives a blue of the first quality;. and the third yields one of less value. The process is founded on the property which the colouring matter of azure-stone has of adhering less firmly to the resinous cement, than the foreign matter with which it is associated. When azure-stone has its colour altered by a moderate heat, it is reckoned bad. Messrs. Clement and Desormes consider the extraction of ultramarine as a species of saponification.*

* AZURITE, the LAZULITE OF Werner and Haüy. This mineral is often found in oblique quadrangular crystals of a fine blue colour. It is translucent only on the edges, brittle, and nearly as hard as quartz. When massive, it is either in grains, or bits like a hazel nut. It occurs imbedded in mica slate. Its lustre is vitreous. Its constituents are 66 alumina, 18 magnesia, 10 silica, 2.5 oxide of iron, 2 lime. It occurs in Vorau in Stiria in a gangue of quartz; but the finest specimens come from the bishopric of Salzburg