Iron oxide particles and process for producing the same

Iron oxide particles comprising:

• 100 parts by weight of iron oxide particles having an area-average particle diameter of 0.1 .mu.m.ltoreq.d.sub.3 .ltoreq.1.0 .mu.m, an area shape factor of 1.0.ltoreq..phi..sub.s .ltoreq.2.0 and a BET specific surface area represented by the formula (1):
• 6/(.rho..multidot.d.sub.3).times..phi..sub.s ( 1)
• wherein .rho. represents the specific gravity of said iron oxide particles, d.sub.3 represents the area-average particle diameter and .phi..sub.s represents the area shape factor, and
• 0.25 to 10 parts by weight, calculated as an oxide, of the fine particles of an oxide, a hydroxide, a hydroxide oxide, a hydrous oxide and a mixture thereof of an element selected from the group consisting of Al, Si, Zr and Ti, which fine particles are adhered to the surfaces of said iron oxide particles,
• the increment of said BET specific surface area of said iron oxide particles being 1 to 6 m.sup.2 /g, and the increment of said BET specific surface area with respect to the amount of said fine particles being not less than 0.35, said iron oxide particles being produced by mixing said iron oxide particles and said fine particles by compressing, shearing and spatula-stroking in a wheel-type kneader.