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COMMON TREMOLITE. 25 on tlie extremities, the bevelling planes set .on the acute lateral edges *. 7. The preceding figure f, truncated on the acute la teral edges. 8. N° 6. truncated on all the lateral edges%. > 9. N° 6., in which all the lateral edges are rounded off||. The lateral planes are longitudinally streaked. The crystals are middle-sized or small; sometimes singly imbedded, sometimes superimposed, or promis cuously aggregated. The lustre is shining, and intermediate between vitre ous and pearly ^[. The fracture is broad radiated, with a double oblique angular cleavage, which gives to the fracture-surface a longitudinally streaked appearance : the cross fracture is uneven 8. The * Grammatitc di-tctraedre, Hauy, + Grammatite bis-unitaire, Hauy. t Grammatitc tri-unitairc, Hauy. || (Irammatite cylindroide, Hauy. % It has a higher degree of lustre than any of the other subspecies. § This mineral splits easily, not only in the direction of the planes of the prism, but also in that of its diagonals, particularly the longest diagonal. When we break across one of these prisms, we observe on the fracturc-sur- facc a line in the direction of the longer diagonal, which is so strongly marked, that at first sight we arc apt to consider it as pointing out these as hemitrope or twin-crystals. The name Grammatite t formerly given to this mineral by llauy, is derived from the character just stated- It is also worthy of remark, that in the fracture of tremolitc, even in prystqls, there is a tendency to the fibrous structure: the stroke of a hammer, or even the simple pressure of the finger in some cases, will separate folia or radia into fibres as delicate as those of amianthus, and which arc somewhat clastic- fierible. All these characters are foreign to hornblende and actypolitc, and Hiay therefore be used as characters for distinguishing tremolite from these species.—-Vide Bournon’s Catalogue Min. p. 87, 88, where all the particu* lars here stated ore more fully enumerated.
