III – Zirconia Alumina:  This grain is gray in color.   Zirconia alumina is most noted for its long life and fast cut rate under heavy grinding stress.  As the grain breaks down under heat and pressure it fractures into smaller jagged pieces.  Zirc, as it’s known in the field, is good at dissipating heat enabling the grain to stay sharp longer than most other manmade and naturally mined grains.   Zirconia alumina is an alloy (mixture) of zircon and aluminum oxide.  Its durability makes this grain extremely effective on difficult to grind and exotic metals such as Hastaloy or Inconel.  (See Fig. 2C)

(Fig 2 C)

IV – Ceramic Alumina:  This reddish-pink colored grain is manufactured from aluminum oxide hydroxide-gel.  The self-sharpening characteristics of ceramic grain offers a constant cut rate during the first 75% of its life.  It excels at medium to high pressure applications. Due to its micro structured grain, the friability is less than that of zirconia alumina but its billions of crystals give this product dependable and measured performance.  These characteristics enable the ceramic grain to offer long life in carbon steels and high nickel alloys.  (See Fig. 3C)

(Fig 3 C)