Occurrence of Transition Metals

Transition metals are, on the whole, considerably less reactive than the s-block metals, and several of them (gold, silver, platinum among the heavier members) occur in the free, uncombined (native) state. The first-row transition metals covered in this chapter, however, mostly occur combined, chiefly as oxide, sulfide and mixed-oxide (spinel-type) ores:

• Titanium occurs as rutile and ilmenite, both essentially $\text{TiO}_2$-based ores (ilmenite is $\text{FeTiO}_3$).
• Vanadium occurs as vanadinite, a lead-vanadate mineral.
• Chromium occurs almost entirely as chromite, $\text{FeCr}_2\text{O}_4$, an iron-chromium spinel oxide -- the starting material for the manufacture of potassium dichromate covered later in this chapter.
• Manganese occurs chiefly as pyrolusite, $\text{MnO}_2$ -- the starting material for the manufacture of potassium permanganate.
• Iron occurs abundantly as haematite ($\text{Fe}_2\text{O}_3$) and magnetite ($\text{Fe}_3\text{O}_4$).
• Copper occurs both in the native (free) state in some deposits and combined as copper pyrites, $\text{CuFeS}_2$.
• Zinc occurs chiefly as zinc blende, $\text{ZnS}$. …