Ngwa ngwa na ihe mejupụtara kemịkalụ enyo enyo na-enwekarị ụdị ngwaọrụ 7-12.E nwere tumadi ájá quartz, soda ash, limestone, dolomite, feldspar, borax, lead na barium ogige.Na mgbakwunye, enwere ihe enyemaka dị ka nkọwa, agba agba, decolora ...
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