However fanciful his theoretical views may be, his classification is not unworthy of praise, and his specific definitions are generally intelligible to a modern mineralogist; but this is nearly all, however, that can be said in their favour. He divides the mineral kingdom into three classes, under the names of Petræ, Mineræ, and Fossilia. These are again subdivided into several orders, and the number of genera amounts to fifty-four.
Class I. Petræ or Stones, or, as modern geologists would say, Rocks.
Steril stones, originating from an earthy principle by cohesion; simple, as being destitute of salt, sulphur, or mercury; fixed, as not being intimately soluble; similar, as consisting of particles united at random.
Order I. Humosæ. Deposited from vegetable earth, combustible and burning to cinders, their powder harsh and light; as roofing-slate.
Order II. Calcariæ. Originating from animal earth; penetrable by fire, and becoming more porous, their powder mealy; and when burnt, they fall into a fine powder; as limestone, marble, gypsum.
Order III. Argillaceæ. Originating from the viscid sediment of the sea, becoming harder and stiffer in the fire, their powder unctuous before exposure to fire; as serpentine, asbestus, mica.
Order IV. Arenatæ. Originating from precipitation caused by rain-water, when struck with steel emitting sparks, very hard, their powder rough and angular like bits of glass; as quartz, jasper, flint.
Order V. Aggregatæ. Originating from a mixture of the foregoing, and therefore participating their constituent particles; their powder differing accordingly; as granite, puddingstone.
Class II. Mineræ, Minerals.
Fertile stones, originating from a saline principle by crystallization; compound, as produced from a stony substance (of the preceding class), impregnated by salt, sulphur, or mercury, intimately soluble in an appropriate menstruum, and crystalline.