Years ago while we were living in Indiana I found this odd “rock”. It looked like a huge tooth, a dinosaur tooth maybe! Or maybe it was just a stalagmite. Anyway it got tossed around here and there among all our stuff. Then the other day my Dad, the resident rock-hound, helped us do an acid test on it to see if it could be a tooth. The battery acid did not affect it at all. So it wasn’t calcium carbonate. Dad said it was probably silica. So much for the tooth theory.

Dad had a slice of a stalagmite; it was very sooth and not at all like our “rock”. The acid test did affect the stalagmite. So it wasn’t a stalagmite either!

Then a few days later I was talking to my mother and picked up a book that I thought was an Audubon Bird book like mine, but it wasn’t, it was an Audubon book of fossils. As I was mindlessly flipping through the pages my eyes just about popped out of my head. There was our funny “rock”.

It is a fossilized coral! A heterophrentis to be exact. Originally it was made of calcium carbonate but over the years it was replaced by silica or quartz.

Much of Indiana is sandstone, so over the years this ancient silica fossil washed free of the surrounding rock, and I found it just laying there!

My son wasn't nearly as interested in this mystry as I was but I hope he did learn something.

I will try to post a picture of it tonight.

Naomi