I found this rock along the shoreline of Lake Ontario in the town of Ajax. It stood out from the smooth pebbles surrounding it and at fist glance I thought it was a piece of concrete. When I picked it up I found it to be surprisingly heavy. The rock measures 100mm x 50mm (4"x2") and weighs 1kg (2.2lbs).
closed as off-topic by Leukocyte, arkaia, Fred, Peter Jansson, Jan Doggen Jul 15 at 17:53
This question appears to be off-topic. The users who voted to close gave this specific reason:
- "Please review our rock identification guidelines to provide the missing information so that your question is both answerable and useful to new users." – Leukocyte, arkaia, Fred, Peter Jansson, Jan Doggen
You don't give the thickness, and with such a rough shape it is difficult to estimate the specific gravity. However, as a rough estimate it seems to have an SG of about 4 to 5.
It is most probably Goethite, an oxy-hydroxide of iron. The colour is exactly right for this mineral, but the density seems too high. The SG of Goethite is variable but generally <4. Try testing it's exact SG. If it really is 4 to 5 then I suspect it has an iron core, in which case it is a weathered and eroded scrap of man-made iron. It doesn't look like a weathered iron meteorite.