Metallogeny of the Japiniese Islands. 



between the Kitakami Valley and the Pacific Ocean. The mines 

 are nearly always in the Paleozoic formation and are associated 

 with such ore-bringers asdiorite, diorite-porphyrite, and sometimes 

 granite. The diorite-porphyrite, green and compact, with 

 phenocrysts not very distinct to the naked eye, is the most favorable 

 rock for ore-deposits. Under the microscope, the felspar is seen to 

 be kaolinized or to form epidote in combination with the decom- 

 position-products of horn].)lende turned into chloritic matter. 

 Magnetite is always present, l)eing particularly abundant toward 

 the margin of the eruptive masses. I observed a very interesting 

 phenomenon between the diorite-porphyrite and the limestone in 

 the Kamaishi Iron Mine. This mine is the most hopeful one in 



A B c 



Fig. 1. — Intrusion of diorite- 

 porphyrite into limestone, in 

 Kamaishi Mine. A, Diorite- 

 l^orphyrite. B, Magnetite 

 crystals. C, Limestone. 



Fig. 2. — Contact of diorite-porphyrite with limestone in 



the Kamaishi Mine. H, Hornblende. E, Epidote. CH, 



Chlorite. L, Limes^on"^. M, Magnetite. 



this province, and is well known as the only private iron-smelting 

 work in Japan. The deposits belong either to the contact of the 

 <liorite-porphyrite with paleozoic limestone, or to that of the 

 diorite-porphyrite with granite, or else the magnetite is wholly 

 enclosed in granite masses. Where the diorite-porphyrite is in 



