THE MINERALS OF IDAHO 325 



to the usual law with the twinning plane a(100) . One crystal showed 



repeated twinning with two narrow lamellae between the two major 



individuals. Many of the crystals shell off in concentric shells 



parallel to all the crystal faces, even the smallest faces preserving 



their luster and permitting good measurements after the surface 



layers have been removed. This shelly structure gives rise to a 



beautiful iridescence on the faces of the crystals and is generally 



associated with a bleaching of the color presumably due to surface 



alteration. Some crystals are embedded in quartz of later growth 



which is the latest deposit in the cavities. Some epidote crystals 



embedded in quartz from the Decorah mine are doubly terminated. 



The forms noted by Palache on epidote crystals from this district are: 



c(001) (103) p(01G) m(210) 



o(100) i(102) n(Tll) x(Tl2) 



/« (102) r(101) 2/(211) d(lll) 



W(305) 1(201) 77(212) 3(221) 



t»(405) 2(110) /(301) 



e(101) o(011) s(203) 



92 

 Figs. 92-93.— Epidote crystals from the Seven Devils district, Adams County. Orthographic 

 projections on 6(010). after palache 



A number of specimens from this district which have been examined 

 by the writer may be briefly described. Chunks of material occurring 

 abundantly scattered over the hill south of the Kleinschmidt grade 

 on the first ridge east of Snake Canyon consist of massive fine-grained 

 epidote forming a dense rock. 



Specimens from the Fidelity claims consist of pale green imperfect 

 prisms and coarse fibrous masses with quartz and calcite and of 

 radiating light pistachio-green prisms in white quartz. 



One lot from the Queen mine dump consists of bright pistachio- 

 green columnar masses in garnet and a second lot consists of im- 

 perfectly crystallized light to dark green masses with well crystallized 

 brown garnet. 



Specimens from the Copper Boy mine consist of masses of large 

 blackish-green crystals deformed by mutual interference. Occasion- 

 ally good terminations project into chrysocolla filled cavities. The 



