Annual report of the State Mineralogist for the year ending ... . odular vein of magnetite twofeet thick (218 and 219). At the southern extremity of the serpentine,between the hill and the Culbertson place, is a considerable outcrop ofmalacolite, or white pyroxene (220). Intrusions often appear in theslates between this point and the river. A mile south of the river thereis an area of coarsely crystalline diorite, with the hornblende in excessof the feldspar (221 and 222). The serpentine is broken into by thisbody of diorite, and is generally laminated. No. 223 is a black, massivevariety. The
Annual report of the State Mineralogist for the year ending ... . odular vein of magnetite twofeet thick (218 and 219). At the southern extremity of the serpentine,between the hill and the Culbertson place, is a considerable outcrop ofmalacolite, or white pyroxene (220). Intrusions often appear in theslates between this point and the river. A mile south of the river thereis an area of coarsely crystalline diorite, with the hornblende in excessof the feldspar (221 and 222). The serpentine is broken into by thisbody of diorite, and is generally laminated. No. 223 is a black, massivevariety. The frequent appearance of long fibrous aggregates (224), rep-resenting the original crystals, is another indication of movement. Several specimens were obtained from the granite dike east of thevein. No. 225 is from its northern extremity. A mile south the dikeis much fresher (226). No. 227 is taken from where the road to Priestscrosses it. At the river the serpentine is four hundred feet wide. Thelode appears again on the south bank, and on the north bank expands. to large proportions. The slates are greatly faulted along the west bankof the river south of Jacksonville. (Fig. 13.) Between the diabase andthe slates at the bridge, there is shown a good section of thin-beddedsandstones. Near their contact with the diabase the bedding planesdisappear, and they become hardened and jointed. The diabase is con- GEOLOGY OF THE MOTHER LODE REGION. 47 siderably decomposed for some distance-. Below the bridge it becomesconglomeritic, the pebbles as well as the matrix being amygdules are also present in the compact, green diabase west of theconglomerate. In some portions the amygdules are small and dark, andthe rock contains much epidote (228). In others they are large andformed of calcite (229 and 230). The texture varies from aphanitic(231) to that of a porphyrite with brown augite crystals in a greenmatrix (232). The lode crosses the river at an altitude of seven hun-dred
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