I say, and with God's success: It is purified by separation. If it is divided, or some of it is washed, or some is given as a gift, or some is sold, then each part will be pure; because it is possible that the impurity is in the other part. This possibility is considered in purity due to necessity, so it is permissible to benefit from all of it due to doubt about it, even if they are gathered, the impurity would return. Refer to: Al-Waqayah and its explanation by Sadr al-Shari'ah, p. 133, and Nafa' al-Mufti and the questioner, p. 162, and Al-Ashbah wa al-Nazair, p. 167, and God knows best.