What is difference between white fused alumina and brown fused alumina?

What is difference between white fused alumina and brown fused alumina?
















Both are materials used for refractory applications(mortars,crucibles,unshaped refractory) or abrasives products(grinding wheels,cutting wheels,flapping discs,polishing media,blasting media). Content of both materials are Aluminium Oxide(Al2O3).
1, Their colors are different. Brown Fused Alumina(BFA) is brown and White Fused Alumina(WA) is white.
2, BFA is made of bauxite and other raw materials in arc furnaces, WA is made of calcined alumina powder in arc furnaces.
3, BFA has Al2O3 content of about 95%,while WA more than 99%
4, WA is harder than BFA although they are both hard(mosh hardness 9), while WA is more fragile.