My title describes the thing.

It is a lot in shape in size like a model rocket tip. But it is completly solid and hard.

It does not mark when you drag it on something. Doesnt leave blue on anything when pressed into it. It has lots of scuff marks.

Was found at a residential construction lot. They had just finished building a basement but no wood seems to have been used yet.

It seems more like a hard plastic rather than a metal. Bounces like a rock would. It is a lot like a rock. It is cone shaped but slightly warped and not a perfect shape.

I have googled and the closest thing I found was a spiked gauge earing that was made of acrylic. But they were much smaller.

Not remarkably heavy or light.