Fiqh-us-Sunnah Volume 1, Purification and Prayer, Fiqh 1.015A.

Section : Purifying mirrors and similar objects.

Mirrors, knives, swords, nails, bones, glass, painted pots and other smooth surfaces that have no pores are purified by simply wiping them and removing any impure remains. The companions of the Prophet used to pray while wearing swords smeared with blood, and they used to just wipe the swords to purify them.