How to identify the quality of corundum brick in the market

Corundum brick has a good chemical stability, acidic or alkaline slag, metal and glass, etc. have a strong resistance, but now the market in the production of many enterprises, so we also have a lot of choice in the main issues, This requires us to have the ability to identify the quality of corundum brick in order to buy high-quality products.(http://www.corundumbrick.net/product/corundum_block.html)
The corundum brick in the market is mainly composed of corundum, corundum has a high corrosion resistance and high temperature characteristics, it is an important refractory brick, widely used in refractory production and processing. Smelting rare precious metals, special alloys, ceramics, iron ore blast furnace lining, another corundum also has a high hardness, good wear resistance, high strength characteristics, can be used in the production of various molds, knives, corundum brick can also made bulletproof material, corundum wear resistance can produce a variety of wear-resistant materials.
The corundum is divided into three grades: the first level of corundum, two and three, the quality of corundum mainly see its Al2o3, its content in the 94.5% -97%, and the other contains a small amount of Fe, Si, Ti Wait. Al2o3 content of more than 95% for the first grade corundum. Two corundum and three corundum content gradually reduced, the quality also will be reduced. Corundum fineness can look at the color to distinguish, because the corundum contains iron elements, iron elements for the reddish-brown, so brown corundum appears to be tan, you can see through the color of corundum brick grade and quality.