Powder, method for producing same, and resin composition containing same

A powder comprising at least one of a spherical silica powder and a spherical alumina powder, wherein a proportion of a number of magnetic colored particles of no less than 45 μm in diameter is no greater than 20% with respect to a total number of the magnetic colored particles of no less than 45 μm in diameter and magnetic non-colored particles of no less than 45 μm in diameter, in a case where a color reaction test is conducted, the color reaction test including steps of:

• (1) preparing a slurry, by way of precisely weighing 50 g of a powder sample and dispersing the powder sample in 800 g of ion-exchanged water;
• (2) obtaining the total number of the magnetic colored particles of no less than 45 gm in diameter and magnetic non-colored particles of no less than 45 μm in diameter, by way of capturing magnetic particles by immersing a bar magnet of 10000 gauss covered by a rubber cover of 20 μgm thickness in the slurry, sifting the magnetic particles with a polyester filter of 45-μm mesh size, counting a number of the particles remaining on the filter;
• and
• (3) wetting the particles by way of dripping 0.5 ml of a mixed solution comprising equal parts of 10% by mass hydrochloric acid water solution, 50% by mass propylene glycol water solution, and 0.5% by mass potassium ferricyanide water solution, on the particles on the filter at a room temperature of 20° C., then leaving to stand for 20 minutes, counting a number of particles thus colored as the magnetic colored particles of no less than 45 μm in diameter, and calculating the proportion of the number of magnetic colored particles of no less than 45 μm in diameter present among magnetic particles of no less than 45 μm in diameter by an equation (Number of magnetic colored particles of no less than 45 μm in diameter)×100/(Total number of magnetic colored particles of no less than 45 μm in diameter and magnetic non-colored particles of no less than 45 μm in diameter).