Being from Utah, I had to know what this is. So I checked ebay. There is one guy on ebay who is selling rocks that are found near his home in Utah. The first rocks I looked at (the gray ones) are called "laced rhyolite" - according to the seller. My uncle is a geologist, so I gave him a call. Rhyolite is a volcanic rock made of silica - so it won't dissolve in your aquarium and should be fine to use.
I only noticed the orange rocks after I got off the phone with my uncle, so I don't know anything about them. But they are described as soft and flaky so my gut feeling is not to put them in the aquarium.
A guy selling rocks on ebay. Now theres an entrepreneur.