What is this cube-shaped rock?

Question

I found all of these cube and rectangular prism-shaped rocks in my yard. They were right near the surface of the dirt. They range from pebble size to quarter size. They are black/dark silverish looking and slightly magnetic. I live in Pennsylvania. Any idea what it might be?

Answer 1

mmmm.... I don't know for sure because you can't really tell what a rock is by appearance alone but the only rock that I've ever seen was cubed and gray, shiny was galena which lead ore and isn't magnetic. mostly though rocks found in nature like that aren't usually just one type of rock. They can be a mixture of different types of rock. So by what you're saying it seems to be a mixture between either galena and magnetite which is very magnetic or galena and hematite which is slightly magnetic. Just keep in mind that it's hard to determine a rock by two properties alone. I've seen hematite (iron ore) in its natural state and it's reddish because of the water over the years creating iron oxide (rust). Hope that helps.

Answer 2

You're right, hematite is hexagonal.  Are your rocks definitely cubic?  Magnetite is octahedral (like 2 pyramids stuck to each other), and does occur in PA.  That would be my best guess.

Answer 3

It's probably hematite.

Hematite is a type of iron ore and it usually appears dark and metallic. It's often used in jewelry, and because of it's composition and iron content it can be magnetized.

EDIT: No, hematite can be shaped any way you need it to be shaped - a pebble, a bead, a spearhead, or even a wedding ring.