Other blocks
Concrete 1/4 CTR Broken
A composite material composed of sand, stone, and cement. This block can not be upgraded and is likely only found in the creative menu.
Harvest drops
Small Stone× 25
Taken apart with a harvesting tool (axe, pickaxe, shovel), before perks and tool bonuses.
When it collapses
Falling, it leaves 
Destroyed Stone (75% of the time) where it lands.