A black solid, B4C, soluble only in fused alkali,
it is extremely hard, over on Moh's scale, rhombohedral;
r.d. 2.52; m.p 2530° C, b.p > 3500° C
Manufactured
by the reduction of boric oxide with petroleum coke
in an electric furnace.
Used largely as an abrasive,
but objects can also be fabricated using high-temperature
powder metallurgy.
Boron nitride is also used as a neutron absorber
because of its high proportion of boron -10.
