Bit Selection Chart

ROCK - DESCRIPTION APPROXIMATE – ROCK HARDNESS Cut and Grind Tools
Conglomerates Hard Shales Limestone Sandstone Extremely Abrasive Broken Faulted Coarse Grained C - 1
Conglomerates Hard Shales Limestone Sandstone Very Abrasive Fractured Medium - to Coarse Grained C - 2
Dolomite Weathered – Granite Peridotite Abrasive Medium - to Coarse Grained Solid to Fractured C – 3B
C - 5
Basalt Diorite Diabase Gabbro Rhyolite Moderately -Abrasive Fine to Medium Grained Solid C – 6
C – 6.5
Pegmatite Feldspar Quartz Granite Skams Volcanics Medium to Coarse Grained Slightly - Abrasive Medium - to Hard C – 7A
C – 7M
Diorite Gneiss Quartzite Granite Solid to Formation Hard to very Hard C – 8G
Diorite Gneiss Quartzite Granite Fine Grained. Non Abrasive - Hard to Very Hard C – 9R
C -10
Jasper Chert Banded iron Stone Glassy Quartzite Very Fine Grained Solid. Extremely Hard Hard - Non Abrasive C – 14