US Aggregate Map & Mohs Hardness Ratings

Aggregate Map of the US

Mohs Hardness*	Aggregate Used in Concrete Mix
8	Very Hard Aggregate (Flint, Chert)
7	Hard Aggregate (Quarts, Hard Gravels)
6	Medium Hard Aggregate (Medium Gravels, Granites)
5	Medium/Soft Aggregate (Soft Granite, Dolomite)
4,3	Soft, Abrasive Aggregate Limestone