Njerwa zapamwamba-zigawika m'magulu a alumina kukhala: Gulu la III (Al₂O₃: 48–65%), Gulu II (Al₂O₃: 65–75%), Gulu I (Al₂O₃: 75–80%), ndi Gawo Lapadera (Al₂O₃: 48–65%), Gulu II (Al₂O₃: 65–75%), Giredi I (Al₂O₃: 75–80%), ndi Gulu Lapadera (Al₂O₃) lofanana ndi ₂O₃.
Zimayikidwa molingana ndi mtundu wa ng'anjo zomwe zimagwiritsidwa ntchito mu: njerwa zamoto-zosasunthika kwambiri-njerwa za alumina zowukira simenti, zotsika-njerwa zotsika kwambiri{3}}zokwera kwambiri{3}}zitofu za alumina za sitovu zamoto, ndi phosphate phosphate yokwera- njerwa za alumina za chitsulo cha rotary kapena rotary za lithiamu kupanga oxide).
Kutengera mawonekedwe ndi makulidwe ake, akuphatikizapo mipeni-zoumbika, -zoboola pakati, -njerwa zooneka ngati mpeni, komanso{3}}njerwa zazitali za alumina ndi njerwa za nangula.
Magulu amaphatikizanso njerwa zokhazikika, njerwa zoumbika bwino, ndi njerwa zoumbidwa mwapadera.