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4 Geology Terms Diamond Drillers Need to Know

posted by Rod McCoremick, Blog author, Fordia Powered by Epiroc

May 14, 2018

Geology is really tied to diamond drilling and although geologists are key players in drilling operations, drillers need to have a basic understanding of geology. The deeper the hole - the more that geological influences become complex. We wrote a blog a while ago on geology basics that drillers should understand. As more and more new drillers and helpers are joining the world of diamond drilling, I thought it would be a good idea to revisit geology and in particular, geological terms that drillers should know.

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Faults are breaks in the earth’s crust caused when one block of ground moves in relation to another one next to it. Faults can be very large and extend for a long distance. They show up in the core as angled breaks. Depending on the type of ground, and because faults are larger, drillers may encounter caving boreholes and other issues.


Fissures and joints

These are cracks that happen in the earth’s crust without any visible movement of ground, and they are much smaller than faults. When these cracks get filled with minerals, you end up with veins. You can see joints and fissures in the core as angled breaks or angles veins. In certain types of ground, water can move along open cracks, dissolve the rock and create large cavities.


Dykes and sills

These are terms that refer to igneous or volcanic rock that have entered, penetrated or embedded into layers of other rock formations. They occur naturally in nature and because they intrude into local or original rock, they are considered as “foreign”. Dykes and sills are also slimmer, younger, and wider than the surrounding rocks or plates. They often have a different color than their surrounding rocks. The difference between them is that dykes are igneous rocks that intrude vertically while sills are the same type of rocks that cut horizontally in another land or rock form. The angle and width of dykes can vary a lot and drilling them can range from easy to very difficult.



A reef is another term for a vein or band of some kind of mineral or ore, and it has nothing to do with biological reefs, like the coral reef. It is a term that is used often in gold exploration.


You are likely to hear the terms above at some point in your life as a diamond driller and it is best to understand what they refer and the difference between them. Problems encountered in ground formation can slow down operations until a solution can be found. Faults and fissures can result in caving boreholes and in loss of water circulation. Solutions are out there to help resolve these problems and you can learn more by checking our resource page or by contacting a member of our technical field support team.