(Sassoline or native boracic acid; boraxsaure), in Mineralogy, the only known compound of boron and oxygen, occurs in white pearly scales, which are soft and greasy to the touch, and have an acidulous taste. It fuses easily in the flame of a candle, and yields a glossy globule, which on cooling becomes opaque if any gypsum be in combination. When dissolved in alcohol it communicates to the flame a fine green tinge; a test which affords the best possible indication of the presence of boracic acid. Its specific gravity is equal to 1.48; and, according to Berzelius, it consists of boron 25.83, and oxygen 74.17. The most celebrated deposit of this substance is the Solfatara, within the ancient crater of Volcano, one of the Lipari isles, where it is sublimated in the form of a thin filament or cake on the surface of the sulphur, and around the fumaroles, whence it arises. These incrustations are composed of small flaky particles, of a delicate silky white colour, very soft, and so greasy to the touch, that a portion invariably sticks to the finger. They are usually not more than an inch in thickness, have sometimes a fibrous structure, and are always more or less tinged with sulphur. It occurs both massive and pulverulent; in which last case the particles form merely a filament or loose covering on the surface of the sulphur, without any attachment or adhesion to each other. Boracic acid is likewise deposited by several of the lagune in Tuscany, and at the hot springs of Sasso, a locality which has procured it the trivial name of Sassoline. The mineral from these deposits, however, differs materially in appearance from that of Volcano. It is grayer in the