There are two known modes of occurrence of hematite and magnetite at the Chichibu Mine, Saitama Prefecture.
One type of hematite occurs as the earliest ore mineral. This type of hematite has been largely transformed into magnetite, especially at the time of formation of earlier pyrite. The other type of hematite is only found within the zone of oxidation product of granular magnetite.
As for magnetite, one type occurs as granular aggregates or well-shaped crystals. Most of them may be of primary origin and may have crystallized out as magnetite during the earliest stage of metallization, but some of them are closely related with the formation of platy magnetite. The other type shows a platy form and may largely be the reduction (hypogene secondary) product of primary hematite.