112 



ECONOMIC GEOLOGY 



the galenite is hydatogenetic (Fig. 70) . According to Thomas and 

 MacAlister the Derbyshire galenite assumes a variety of forms 

 which they have classified as rakes, pipes, flats and serins. The 



UKKKX.MMO.3iTt @oB 



FIG. 70. Section exposed in a breast of the Enterprise mine at Rico, 

 Dolores County, Colorado. (After Richard.) 



rakes are true fissures, often faults; the serins are mineralized 

 fissures crossing them; the flats are mineralized bedding planes; 

 the pipes are irregular pipe-like bodies of ore. 



FIG. 71. Ideal section through flats and pitches of the lead and zinc region 

 of Wisconsin. (After Chamberlain.) 



In the United States, lead minerals occur in veins which may be 

 tilted^to almost any angle with the strata which the fissure vein 

 traverses. In Missouri, galenite occurs filling large cavities as 



