I am not sure if this is quartz. I don't know much about quartz but this rock I have is brittle and believed to be quartz and was found with many others that looks similar. I have been looking for a rock that I can start a fire with. If this is a quartz rock then what type of quartz is it?
The smoky color of quartz is commonly the result of gamma ray bombardment form nearby uranium mineralization (or sometimes potassium or thorium), over millions or even billions of years. The quartz itself does not become radioactive from this process, its crystal structure is merely altered to give it the smoky color. When you go for a chest xray or a dental xray, your body doesn't become an xray emitter, its the same process for gamma radiation. The object that is being irradiated does not become radioactive. If you've got ceramic toilets, gypsum wallboard, or granite countertops in your home, those will emit more gamma rays then the smoky quartz ever will. You have nothing to worry about.
It can only be dangerous if you throw it at someone. I have a piece of petrified wood from the Windgate formation in southern Utah. It is mostly brown with black streaks. The black is uraninite, (aka uranium oxide) but even the radioactive mineral does not give off enough radiation to be dangerous. Dont over think it, your smoky quartz probably was irradiated (either naturally or artificially) but neither the silica, oxygen nor trace metals are radioactive.
Most smoky quartz is smoky naturally. I think your friend has fallen into the social fad of taking myth for truth. I wouldn't worry about a thing. don't psych yourself out because then you will get sick.
All quartz makes fines weapons, thrown as chunks or splintered into sharp knives, spear and arrow tips. But irradiated, no. It is possible, of course, but no one does it. Smokey quartz is very common form of quartz, there is no commercial reason to treat it for sale.
