Complex sentence: Everett registered a claim to the site and had samples of the ore assayed; the ore proved to be of high quality, specifically hematite with a small percentage of manganese and chromium, and the Jackson Mining Company switched its focus from copper to iron.
Split into simpler sentences: Everett registered a claim to the site and had samples of the ore assayed; the ore proved to be of high quality, specifically hematite with a small percentage of manganese and chromium. The Jackson Mining Company switched its focus from copper to iron.