Technology: how a metal detector works

The tutor gives a nontechnical explanation of how a metal detector functions.

Watching Curse of Oak Island on the History channel, you see them use metal detectors.

How does a metal detector work? A basic explanation is this:

  1. The search coil has electricity passing through it so that it emits a magnetic field.
  2. A characteristic of metals (as opposed to nonmetals) is that their electrons are moved by a magnetic field.
  3. As the metal object’s electrons move, they change the electromagnetic environment. It’s a kind of “rebound” effect.
  4. The detector has a detection coil that senses the electromagnetic rebound broadcast from the movement of the metal’s electrons.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Minerals: what is corundum? Rubies in Cape Breton, Nova Scotia

Tutoring science, one might expect questions like these more often. The tutor seeks the answer to another childhood curiosity….

I remember seeing Mohs’ hardness scale when I was a kid. On it, quartz is 7, corundum 9, and diamond 10.  I think in grade five, we spent a week on minerals.  Additionally, we watched educational films on Thursday afternoons; eventually, one happened to be about minerals.

I was never interested in minerals as a kid, but I knew there was a big world about them for those who were.  In the film we saw about them, the voice said, “The hardest mineral you’ll probably find is quartz.”  Having lived on rocky coastal areas much of my life, I knew I’d seen quartz already.  Corundum, however, was among the minerals of which I’d never heard.  Why, I wondered, would I not find it?

The week ended, life continued, and I soon forgot about finding corundum.  I was eleven years old, living in Nova Scotia.  While I never found corundum, someone else did.

Corundum is the mineral that makes sapphires and rubies. In an article dated 2005, Hans Durstling tells of the discovery of rubies in Cape Breton, Nova Scotia. The discovery was, ironically, in a quarry that had produced dolomitic limestone for twenty years. He points out that rubies would likely have been shipped out in the limestone, overlooked.

Nova Scotia is a geological curiosity for more than one reason. I don’t know much about it, but I hear bits and pieces.

I’ll be discussing geology, Nova Scotia, corundum, and other minerals in future posts. Like the discovery of rubies in Cape Breton, this topic is a rich find that comes from re-examining the past:)


Wolley, Alan. Spotter’s Guide to Rocks and Minerals. New York: Mayflower Books,   1979.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.