To provide spindlelike metallic magnetic particle powder having suitable coercive force while being fine particles and good in dispersibility and oxidation stability and to provide goethite particle powder and spindlelike hematite particle powder as the starting raw materials therefor.

The spindlelike goethite particle powder containing <0.5 to 6 atomic% Co and >10 to <20 atomic% Al, and in which the ratio of Al/Co is >2 to 4 is obtained, at the time of aging water suspension containing primary iron-containing precipitates obtained by reacting a mixed alkaline solution with an aqueous solution of ferrous salt, thereafter forming spindlelike goethite seed crystal particles by oxidation reaction, passing an oxygen-containing gas through the inside of the seed crystal particle-containing water suspension and growing a goethite layer on the surfaces of the seed crystal particles to form spindlelike goethite particles, in the case of the aging, in the period of 1/2 of the total aging period, by adding a Co compound, performing the oxidation reaction in the range of 40 to 50% of the total Fe2+ and next adding an Al compound.