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'Cannon Ball' Erratic

Submit an Entry: My Metamorphic Rock

By Glen E Smith

'Cannon Ball' Erratic

My Cannon Ball

Where This Rock Is From (place, type of locality, etc.)

This rock is from my property in South Frontenac Twp. Ontario, Canada, on the Canadian Shield

What This Rock Is

This rock is igneous or granite. It probably boiled out of the Earth's mantle about four-billion years ago in the James/Hudson's Bay area. Meteor strikes, later, smashed much of that area producing millions of jagged rocks that were picked up by the glaciers and ground smooth on their journey South. I'm not sure if we can refer to this stone as a true 'erratic' as the underlying bedrock is composed of a similar material. Eastern & Southern Ontario was 'gifted' with millions of rocks like this as one sees along farmer's fields. We commonly refer to them as 'hardheads' and 'fieldstone.'

What I Like About This Rock

I have brought about one-half dozen rocks home over the years and this one is my favourite. It came out of the ground where I was setting a fox-trap years ago. I refer to it as 'my cannonball.' It's about the size of a five-pin bowling ball. It stays on my bedroom shelf and only comes out if I need a weight to hold a turkey that I'm brining under the solution. I'll probably have to make a special note in my will to make sure that it has a good home after I leave.


  • I am at best a very, amateur geologist. I have a casual knowledge of rocks in this area but much prefer to spend my time thinking about how they got here. There are so many unanswered questions. The geologists in Ontario seem to be as stolid and unmoving as the rocks that they study. I was vastly pleased to learn that the people working with rocks in the state of Michigan are much more forthcoming in their outlook. Thank you for letting me share. :-) Glen

Andrew Alden, About.com Geology, says:

It's hard to tell much about this stone, but anything from the Canadian Shield has an extremely long history, and the odds are overwhelming that it's undergone some metamorphism in that time.
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