The result of the chemical analysis made for the lepido-melane, forming one of the essential ingredients of garnet-lepidomelane-quartz-fels, is given in Tab. 1. From this analysis, a chemical formula can be written as
(OH)_2.95 (Fe'', Fe''' Mg, Mn, Ti, Al)_3.08 [(Si, Al)_4.00O_10.00] (K, Na, Ca)_0.97.
The total content of iron oxide as FeO is 30.20%, in which Fe₂O₃ is 7.81%. These percentages and the ratio FeO: Fe₂O₃ are comparable with those of lepidomelane from Miask¹⁵⁾ and also with those of biotite from Beech Hill¹⁷⁾. The pleochroic colours change from light brown to deep brown and the refractive index is given as γ=1.662, which is smaller than that of biotite from Beech Hill, as seen in Tab. 2.

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The gold and copper deposits of the Daté mine, Hokkaido, are found in the Tertiary liparitic and propyritic rocks and their breccia tuffs. The largest of them is the Tsudô deposit, which is irregular in shape and is made of fine-grained aggregates of pyrite with some tetrahedrite, bornite, chalcopyrite and gold. In the central part of the deposit, the ore mainly fills up the interstices of silicified and partly pyritized fragments of country rocks, often crustifying the fragments in a, form of “ring ore”, while in the marginal parts the ore traverses the less silici-fied rocks in a form of network. The content of gold and copper is higher in the central portions.
Surrounding this deposit, several other deposits of different types are found in much smaller scales. Some of them are irregular veins and pipes along some fault planes and were worked for gold or for copper, while the other was prospected for galena and zincblende, disseminated in altered clayey rocks. Some veins are rich in gold-telluride, and are highly characterized by extremely high tenor of gold. A purple mineral, fibrous and highly pleochroic under vertical illumination, is also found along the margin and fractures of telluride. The mineral changes, upon strong fusion, to gold globules. It seems to be an alteration product of gold-telluride, but its properties are not in accord with any minerals, ever known.

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