ABSTRACT
Quartz 280 240-340 19.3 15.3-24 75 80-100 Very abrasive, homogeneous Andesite 190 150-240 17.9 12.0-24 27 24-30 High strength, fine grained Sandstone 170 25-320 17.3 5.1-31 60 30-90 High abrasiveness, massive Granite 170 85-285 13.8 7.8-23 45 30-60 Hard and massive few cracks Basalt 145 50-280 14.0 7.3-23 24 17-30 Little abrasiveness, fissures Limestone 130 75-270 11.9 6.0-19 5 <5-15 Non-abrasive, brittle Slate or Schist 110 55-250 13.6 9.3-31 39 15-75 Fissures and cracks present Siltstone 95 30-180 8.5 4.1-19 15 5-33 Inhomogeneous
• Shale is the commonest sedimentary rock – characterised by its laminations. • Mudstones are similar grain size as shales – but non-laminated. • Shale may contain significant quantities of carbonates.
