Possible Clues:

• Sedimentary rock
• Rock fans nod assent
• Type of sedimentary rock
• Building material carried by thousands to neighbourhood
• The hard sound of S with S?
• Rock formed of compacted and hardened grains
• Such building material sets, and no mistake!
• Gives a smooth finish to sound building material
• Among the best of building materials, one stands out
• It's hard to get the gritty sound of this