HRC50
|
Soft
|
Medium
|
Clay, Shale, Siltsone, Cypsum
|
HRC48~50
|
Soft
|
Very high
|
Ash stone, coal, Argillite, Vocanics, Sandy pebble
|
HRC45~48
|
Medium soft
|
Very high
|
Sandstone, sandy shale, Lithoid, Limestone
|
HRC40~45
|
Medium
|
High
|
Medium-hard limestone, medium-hard shale, medium hard ash stone
|
HRC38~42
|
Medium
|
Medium
|
Marble, hard schist, hard streak stone
|
HRC38
|
Medium hard
|
Medium
|
Diabase, andesite, gneiss
|
HRC35~38
|
Medium hard
|
Medium
|
Grandiorite, limonite
|
HRC32~35
|
Hard
|
Medium to low
|
Granite, basalt, hard streak stone
|
HRC25~30
|
Hard
|
Medium to low
|
Rhyolite, gneiss, quartz porphyry
|
HRC20~25
|
Extreme hard
|
Medium to low
|
Silicious stone, hard sandstone
|
HRC10~20
|
Ultra hard
|
Low
|
Rhyolite, dense quartzite, iron stone
|
