GEOLOGY AND ORE DEPOSITS OF SU-AN 11 



radiating needles (figs. 1 and 2). It is opaque and submetallic, appear- 

 ing just like stibnite for which it has been taken. The cleavage toward 

 (001) is distinct (fig. 2), especially after partial solution. Before the 

 blowpipe the isolated ilvaite gives no reaction for sulphur, but a reac- 

 tion for manganese. On careful examination of the thin needles the 

 mineral turned out to be transparent breislakite-like, emerald-green 

 needles. Absorption pronounced ; c > n or b, a brown, c sap-green ; 

 and on account of strong absorption the needle becomes black in the 

 latter direction. The optical character is positive. The refraction is 

 high ; but the double-refraction \veak. 



Cg) The extreme modifications (PI. II. figs. 3 and 4 ; PI. III. fio-s. 

 1 and 2) of contact metamorphism are represented ])y the diopside-rock 

 and garnetite, both being parts of the ore-body. The («) diopside- 

 rock ^^ is a compact, fine-granular variety of a light grayish-yellow 

 and sometimes pistachio-green color. Under the microscope, it is 

 entirely made up of prismatic-granular, grayish-white diojDside (PI. IL 

 figs. 3 and 4). It is frequently twinned after (100), and has the coarse 

 but distinct prismatic cleavage of augite. From the outline of the 

 basal section the crystal seems to be bounded by both pinacoids trun- 

 cated at the four corners by prismatic faces. Extinction-angle c : c is 

 over 40°; double-refraction strong. Prismatic termination is resolved 

 into stiff needles which are colored light-green and show differences 



slides. The diopside usually avoids proximity to ilvaite (PI. I. fig. 6) which in turn seems to 

 prefer the presence of calcite (see the same figure). The diopside and copper sulphide (Pi. 

 II. figs. 3 and 4), the ilvaite and sulphide ores occur in association, so also the diopside 

 and muscovite. There is no iron-pyrite in the present ore- body ; but if both iron-pyrite and 

 copper-pyrite are present at the same time, the latter serves as a cementing matrix for tlie 

 crystals of the former, as is well seen in the ore-body of the Hitachi (0 jIa^ cojiper mine in 

 the province of Hitachi, Japan. 



1) The diopside rock or diopsidite, wliich is usually called salite rock by our economic 

 geologists, is not necessarily a lime-silicate-hornfels, though in a majority of cases it is a 

 product of contact-metamorphism produced upon limestone by a salic eruptive. The writer 

 once saw it occurring in a lenticular shape impregnated with workable copper-sulpliides in 

 graphite-schist at the Yoshioka Mine (-(Jlt^^IiBII^lll) in the province ofBitchû (Japan). At 

 the Sasano Mine in the same mining region we find an extensive development of a light- 

 greenish, flinty diopsidite as the country-rock of the copper ore-body at its contact with 

 graniteporphyry. The diopsidite here seems to be a contact-metamorphosed slaie. 



