What is the difference between screened, minus and washed rock?
The classes of rock are based around the amount of fines – dirt which goes through the screening process and ends up in the final product – they contain. The three most common classes are minus, screened and washed. ‘Minus’ rock can contain up to 80% fines, making it look more like a pile of dirt with some rocks than the other way around. ‘Screened’ rock typically contains between 20% and 40% fines. The cleanest, or most ‘pure,’ rock is ‘washed’ rock.
