ʻO Silicon slag kahi huahana o ka hoʻoheheʻe ʻana i ke silika metala a me ka ferrosilicon. He ʻano scum e lana ana ma luna o ka umu i ke kaʻina o ka hoʻoheheʻe ʻana i ka silicon. ʻO ka maʻiʻo mai 45% a 70%, a ʻo ke koena he C, S, P, Al, Fe, Ca. He ʻoi aku ka maikaʻi ma mua o ka metala silika maʻemaʻe. Ma kahi o ka hoʻohana ʻana i ka ferrosilicon no ka hana kila, hiki iā ia ke hōʻemi i ke kumukūʻai.