. Un traité sur les roches, les sols et l'altération des roches ;. Pétrologie ; les sols. 108 BOCKS aqueuse. Fig. 8.-partiellement modifié à pyroxène serpentine. Plusieurs variétés de serpentine sont généralement reconnus. Serpentine noble ou précieux est simplement une très compact pure va- riety d'une profonde oil-jaune ou vert. Amianthus, ou tiUf chryso- comme indiqué ci-dessus, est le nom donné à la variété fibreuse. WilUamsite est une profonde couleur vert vif, trans- lucent, et quelque peu variété écallieuse, oc- curring associées à la chrome dépôt de fer dans Fulton Township, comté de Lancaster, Pennsylvanie. Deweylite est un disque, transluce

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. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. 108 AQUEOUS BOCKS. Fig. 8.—Pyroxene partially altered to serpentine. Several varieties of serpentine are popularly recognized. Precious or noble serpentine is simply a very pure compact va- riety of a deep oil-yellow or green color. Amianthus, or chryso- tiUf as noted above, is the name given to the fibrous variety. WilUamsite is a deep bright green, trans- lucent, and somewhat scaly variety, oc- curring associated with the chrome iron deposits in Fulton township, Lancaster County, Pennsylvania. Deweylite is a hard, translucent variety occurring in veins in altered dunite beds. Bowenite is a pale green variety forming veins in limestone at Smithiield, Rhode Island. PicroUte, marmolite, and retinolite are varieties of minor importance. Serpen- tine alone, or associated with calcite and dolomite, forms a beautiful marble, to which the names verd antique, opiate, and opJiiohte are given. The so-called Eozoon Canadense, a supposed fossil rhizopod, is a mixture of serpentine and calcite or dolomite. The name serpentine is from the latin serpentinus, serpent-like, in allusion to its green color and often mottled appearance. Those serpentines which were derived from basic eruptives, or complex metamorphic rocks are described with those rocks with which, in their unaltered state, they would naturally be grouped. The mineral steatite, or talc, when pure, differs from ser- pentine in containing 63.5% of silica, 31.7% of magnesia, and 4.8% of water. Its common form is that of white or greenish inelastic scales, forming an essential constituent of the talcose schists. As is the case with serpentine, it sometimes results from the alteration of eruptive magnesian rocks, such as the pyroxenites, and rarely occurs as a direct result of precipitation. Pyrophyllite, or agalmatolite, is a hydrous silicate of alumina, somewhat harder than talc, which it otherwise resembles, and which is used in making slate pencils

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