The calcareous tuff impedes the bloating process of lightweight aggregate production. At 2,000° F (1,100° C) the calcite simply calcines. At high temperatures of over 2,200° F (1,200° C) diabase rock (specific gravity of 3.0) begins to melt to a glassy type of rock with no specific gravity change. Because this high specific gravity creates havoc on a desired lightweight specific gravity material, it should be avoided.

The only way to avoid this material is through a process of selective mining. Extensive core drilling must be performed along with microscopic, chemical, and laboratory test bloating of the core in order to “map” the subsurface material and identify desirable versus non-desirable aggregate. Computer software must then be used to identify high-quality cross-sections of desirable versus non-desirable rock zones. Mining computer software can then be used to design the selective mining sequence. A modern fractionating plant with controllable radial stackers and feed systems then crushes the high-quality bloatable material to optimum size for processing, separates it, and then conveys it to the raw feed storage silos [4].