Been awhile since I checked in. I received a metal detector for christmas, and while I was out I found this rock.
Just curious what it may be. Looks a lot like the piece of petrified wood I found in the past, but much darker in color. Sounds like glass when you tap on it.
thanks

My guess is either obsidian or Smokey quartz.

I think you are correct that it is a piece of petrified wood. Most petrified wood (especially in Colorado) is a form of Quartz called Chalcedony. This mineral is basically quartz, with crystals so small that you can only see them under a microscope. All kinds of impurities can be locked in the chalcedony, causing a wide variety of colors including brown/ tan, red, green, yellow, black, and so on. Your piece that you found is simply a very dark brown type of chalcedony, often known as Flint, and was commonly used for arrowheads and spear tips by ancient man. Some flint is also good for making fire( by striking the rock to make sparks). Your specimen looks like it would make an excellent arrowhead. Other common names for chalcedony similar to yours are Jasper/ or Agate. Yours is a nice sample, good find!

Thanks for posting the pics, Jay - I have a piece exactly like this, I too wondered what it was. And thanks for everyone's input!



RhodoRose