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Cemex officials said the company plans to lower emissions in part by using clinker substitutes that are byproducts of other industrial processes, such as burnt shale oil or glass furnace slag.

Fifty tons of this burnt shale are required to make one ton of alum.

Of these, oyster or marine shells, burnt shale, and slag are most common.

Its base consists almost entirely of pumice, in which are included fragments of basalt and other lavas, pieces of burnt shale, slate, and sandstone, and numerous trunks and branches of trees.