Published June 23, 2015

Terms You Need to Know: Strike and Dip

TYNK is becoming a regular column on our portal that will feature articles on the nuts and bolts of mining and resource investing.

We’ll kick off our series with a review of strike and dip.

Mineralized rock is so dense not even Superman can see through it. The solution? Think in three dimensions. Understanding what’s on top of what and how things are oriented can help us figure out where to look. That’s where strike and dip come in.

Strike

When you stand on the surface over a mineral deposit, it’s almost always going to be longer in one direction. That direction is the strike. This is true whether we’re talking about distinct veins, crazy swarms of veinlets, or lenses in different orientations.

Dip

When you stand on the surface over a mineral deposit, it pretty much never extends straight down under your feet. Even if it’s only slight, there’s an angle. That angle is the dip.

Why Is This Important?

The strike tells us which way the mineralization is going. It helps us follow the mineralization on surface and predict where to find more. This is particularly useful if it has been covered on the surface with younger rocks, gravel, plants, etc.

Likewise, the dip tells us which way to look for more mineralization as we probe farther down into the ground. This is crucial, since getting the dip wrong can cause us to drill right over or under mineralization.

Ideally, a drill hole should be oriented perpendicular to both strike and dip. This is how we get the best understanding of the target and its true width. If you hit it at an angle, mineralization will seem wider than it really is.

A company press release may say that a zone of mineralization is open along strike. This means that exploration to date has not found the end of the mineralization. More of it may be discovered along the strike of the known zone. If drilling on both ends of the known mineralization has come up dry and closed it off, the only direction to find more is down.

When a mineralized zone is open at depth, you’ll see it described as open “down-dip.” That’s not a bad thing in itself. But the deeper you go, the more expensive it gets.

Bonus Term

There’s a third, less used word that describes the orientation of mineralization: plunge. Plunge is much like dip; but unlike dip, it’s within the same direction as the strike. Many deposits are roughly planar and have no visible plunge to them. Yet where there is a clear plunge, it’s very important for finding more mineralization.