Mica powders were pulverized by two methods yielding respectively granular and flaky particles. The mica particles were made hydrophobic by using a silane-coupling agent, and their properties as emulsifying agents were investigated. The hydrophobic mica particles formed stable O/W type droplets but not W/O type droplets. The droplet size decreased from several hundred millimeters to below one hundred micrometers with increase in the added amount and decrease in the size of mica particles. Further, when added in the same amount, flaky particles formed smaller droplets than granular particles. Droplets of styrene were formed using the mica particles and polymerized by UV irradiation. SEM photographs of the polystyrene beads suggested that the mica particles are adsorbed on the organic-aqueous interface with their flat plane lying on the interface.