Cov hlaws dai uas ntab yog cov pob zeb uas muaj cov tshauv ya uas ntab tau saum npoo dej. Lawv yog xim grey-dawb, nyias thiab khoob, thiab hnyav sib dua. Qhov ceev ntawm cov khoom yog 720kg/m3 (hnyav), 418.8kg/m3 (sib dua), thiab qhov loj ntawm cov khoom me me yog li 0.1 hli, qhov chaw kaw thiab du, qhov thermal conductivity me me, thiab qhov refractoriness yog ≥1610 ℃. Cov tshuaj lom neeg ntawm cov hlaws dai uas ntab yog feem ntau yog silicon dioxide thiab txhuas oxide. Nws muaj ntau yam ntxwv xws li cov khoom me me, khoob, lub teeb yuag, muaj zog siab, tiv taus kev hnav, tiv taus kub siab, rwb thaiv tsev thermal, rwb thaiv tsev thiab hluav taws kub retardant. Nws yog siv dav hauv ib qho ntawm cov khoom siv raw rau kev lag luam refractory.