48 



BULLETIN OF THE 



crystals of actinolite. Besides actinolite, the chief constituent, it also 

 contains magnetite, garnet, and a little hematite. The garnet contains 

 inclusions of actinolite. The garnetiferous rock (97) adjacent to the 

 granite (p. 52) is composed of actinolite, quartz, garnet, and a little 



secondary hematite. 



Southeast of the Old Washington mine a dike was seen breaking 

 irregularly through the schists. Near the centre of the dike, the rock 

 (305)' resembles a chlorite schist, but is composed of actinolite, mag- 

 netite, quartz, biotite, and muscovite, none of which appear to be 

 original constituents, except perhaps the magnetite. A specimen near 

 the exterior (306) was more massive, but contained the same min- 

 erals. Part of the iron showed the decomposition of titanifcrous iron. 

 No. 307, from the edge of the dike, closely resembles a ehloritc schist, 

 and contains garnets and well-formed crystals of tourmaline. No. 308 

 comes from the edge of the dike, and is so filled with garnets as to 

 resemble eklogite. Neither of the four specimens would macroscopi- 

 cally be. taken as belonging to the same rock if their relation was not 

 known. This is probably the rock described by Dr. Wichmann as eklo- 

 gite.* The schist at the point of contact is much indurated and quartz- 

 ose, and the garnets make an irregular columnar mass adjacent to it 

 (309). They are so crowded and drawn out at right angles to the schist 

 that their structure very closely simulates the prismatic structm-c of a 

 basaltic dike. Such structure and arrangement of minerals, in a ring, 

 parallel to the surfjxce of the enclosed fragment, is frequently seen about 

 quartz grains and other foreign materials included in the volcanic rocks 

 of the Cordilleras. Several other dikes of the same rock were seen 

 near this. All were very much contorted, breaking very irregularly 

 through the schist, and showing intrusive characters. 



The actinolite schist south of Humboldt was seen to pass into a quartz- 

 ose rock made up principally of alternate layers of quartz and actinolite 

 (319, 320). This shows very conclusively the sedimentary origin of the 

 schist here. The banded magnetic schist of Mr. Brooks southeast ot 

 the Champion mine (No. 348, p. 57) is seen microscopically to be com- 

 posed of a thick mat of actinolite holding garnet, quartz, and magnetite. 

 The magnetite is surrounded in many cases by thin films of hematite, 

 derived from the magnetite, and extending between the actinolite crys- 

 tals. The same hematite films extend around the garnet and penetrate 

 along its fissures, giving it a deep red color, but leaving the centre often 

 clear. Only a little quartz was observed. 



* No. 1091, Gcol. of Wise, IIL 649. 



