Provided is an external preparation for skin that is produced by purifying and liquefying hot spring mineral deposits originating from a sulfurous spring containing alum, and that is for use in bath additives, lotions, relieving skin diseases, and the like. The external preparation for skin comprises a filtrate that is obtained by: dispersing mineral deposits in water, said mineral deposits being formed by passing steam from a sulfurous spring through a clay layer containing alum and using the remaining clay that was used to form the mineral deposits as a filter material to filter the resulting dispersion liquid. The mineral deposits are either only red, yellow, or white mineral deposits, or are a mixture of an appropriate combination of two or more of these mineral deposits. The filter material may be used to fill a non-woven bag that is used as packaging for mineral deposits when selling alum spring mineral deposits.
