To understand the answer, we need to know something about the rocks’ weight. This is not straightforward because rocks have different complex shapes, and different mineral compositions with varying densities. However, the weight of a rock increases significantly as its diameter increases, as shown in the table below.

The rock size defines the crusher gap: a) Minimum crusher gap. b) Maximum crusher gap.

Blast rock Primary cruscher Secondary crucher
 Size  Maximum: 600-1200 mm (24—42”) Minimum: 250 mm (10”)
Maximum: 500 mm (20”) 		Minimum: 50—100 mm (2—4”
 Weight Maximum: 183–1460 kg (403–3219 lbs.) Maximum: 140 kg (309 lbs.) Nominal: 7 kg (15 lbs.) 

Typical stone sizes and weights for blasted and crushed rock.

Typically a dump body is loaded with a mix of rocks, sand, clay and water and contains voids, so the rock density is not directly proportional to the volume of the body. A typical density for crushed aggregate is around 1600 - 1800 kg/m3 (100 – 112 lb/ft3) and the density of granite is 2520 - 2810 kg/m3 (157 - 175 lb/ft3). Because the largest rocks are the ones that cause dents, the rock density is worthwhile considering. Other properties, such as toughness, will also play an important role in dent resistance.

Rock type Density in kg/m3 (lb/ft3)
 Quartz  2650 kg/m3 (165 lb/ft3)
 Magnetite  5180 kg/m3 (323 lb/ft3)
 Hematite  5260 kg/m3 (328 lb/ft3)
 Feldspar  2550—2760 kg/m3 (159—172 lb/ft3)
 Limestone  1550—2750 kg/m3 (97—172 lb/ft3)
 Granite  2520—2810 kg/m3 (157—175 lb/ft3)
 Concrete  2000—2400 kg/m3 (125—150 lb/ft3)
Rock type
 Quartz
Density in kg/m3 (lb/ft3)
 2650 kg/m3 (165 lb/ft3)
Rock type
 Magnetite
Density in kg/m3 (lb/ft3)
 5180 kg/m3 (323 lb/ft3)
Rock type
 Hematite
Density in kg/m3 (lb/ft3)
 5260 kg/m3 (328 lb/ft3)
Rock type
 Feldspar
Density in kg/m3 (lb/ft3)
 2550—2760 kg/m3 (159—172 lb/ft3)
Rock type
 Limestone
Density in kg/m3 (lb/ft3)
 1550—2750 kg/m3 (97—172 lb/ft3)
Rock type
 Granite
Density in kg/m3 (lb/ft3)
 2520—2810 kg/m3 (157—175 lb/ft3)
Rock type
 Concrete
Density in kg/m3 (lb/ft3)
 2000—2400 kg/m3 (125—150 lb/ft3)

Weight of granite rock of different sizes.