It is generally known that the diamond is pure carbon (charcoal is carbon in an impure state), but it is not as generally known that the ruby and the sapphire, “two of the most beautiful gems with which we are acquainted, are composed almost solely of alumina,” or pure clay in a crystallized state.
Silicious.—An earth composed largely of silex. Silex or silica is considered to be a primitive earth constituting flint, and containing most kinds of sands, and sandstones, etc. China or porcelain, ware is formed from silica and alumina united, i. e. from silicious sand and clay.
Calcareous.—A soil into the composition of which lime enters largely. Limestone lands are calcareous. Pure clay manured freely with marl becomes calcareous, for marl is, mostly, clay and carbonate of lime.
Alluvial.—Strictly speaking, alluvium or our alluvial soil, is a soil formed by causes yet in existence. Thus a bottom-land is formed by the wash of a river. It is usually a mixture of decayed vegetable matter and sand.
Diluvial.—A diluvial soil or deposit is one formed by causes no longer in existence. Thus a deposit by a deluge is termed diluvial. The word is derived from the Latin (diluvium), signifying a deluge.
The terms argillaceous, calcareous, silicious, alluvial and diluvial are constantly employed in all works which treat of husbandry.
Friable.—A friable soil is one which crumbles easily. Clay is adhesive, or in common language clammy: leaf-mold
is friable, or crumbling. Clay becomes friable when, by exposure to air or frost, or by addition of sand, vegetable matter, etc., it is thoroughly mellowed.