Impregnated diamond core bit ~ Hardness Selection Sheet

Matrix Hardness

Rock Hardness

Abrasiveness

Rock Type

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