CHLORITE GROUP. ay 
schist or slate ; and they give rise also to chloritic varieties 
of other rocks. Moreover, chlorite is a result of the altera- 
tion of pyroxene, hornblende, and some other iron-bearing 
minerals; and pyroxenic igneous rocks, like doleryte, are 
often strongly chloritic (as revealed by the microscopic 
examination of thin transparent slices), in consequence of 
this alteration—but alteration that took place before the 
rock had cooled. Such green chloritic material, where the 
species is not determinable, has been called Viridite. The 
cavities in amygdaloid are often lined, and sometimes filled, 
by a species of chlorite, which was made from certain con- 
stituents of the amygdaloid in the manner just stated ; and 
the rocks adjoining trap dikes are at times penetrated by 
chlorite made in them by means of the heat, and the mois- 
ture contained in them or ascending with the erupted rock. 
Pyrosclerite. 
Trimetric or monoclinic. Mica-like in cleavage; folia 
flexible, not elastic, and pearly in lustre. Color apple-green 
to emerald-green. H.=3. G.=2-74. 
Composition. (Mg, ZAl), O1.8i,+3 aq=Silica 38°9, alu- 
mina 14°8, magnesia 34°6, water 11°7=100. B.B. fuses to a 
grayish glass ; gelatinizes with hydrochloric acid. 
Obs. Occurs in serpentine, on Elba. 
Chonicrite (Mctaxoite) is related to the above in composition, but 
affords 12 to 18 per cent. of lime. 
Vermiculite. 
Mica-like in cleavage. Grayish, brownish, and yellowish- 
brown in color. In aggregated scales. Also in large mi- 
caceous crystals or plates. Lamine flexible, not elastic. 
Lustre pearly. 
Composition. Mv, (Fe,Al) O. Si; When heated it exfo- 
hates, and when scaly-granular the scales open out into 
worm-like forms; and thence the naime, from the Latin 
vermiculor, I breed worms ; B.B. fuses finally to a gray 
mass. From Milbury, Mass. 
Jefferisite is a similar mineral in composition and exfoliation, occur- 
ring in broad folia. Composition };Mg,i(Fe,,Al,)O,,Si,. From veins 
in serpentine in Westchester, Pa. Culsayeeite from Culsagce, North 
