Ahoy. I picked up some quartz and some other translucent rocks on the railroad tracks today. The outside is stained with some yellow stuff that won’t wash off. I was wondering how I could get these rocks looking clean, preferably with some household items.
Hydrochloric acid works pretty well on iron stains. You can pick it up at any hardware store. It’s usually called Muriatic acid there.
I’ve not tried it, but toilet bowl cleaners with glycolic acid should also work.
Give your rocks an overnight soak, and wear gloves if you decide they need acid scrubbing.
Excellent. I did find some “Zap!” stuff which has hydrochloric acid in it. I hope it’s not too diluted, since it doesn’t list a percentage of content. It also contains sulfuric acid. That won’t hurt SiO2, will it?
Neither sulfuric acid nor hydrochloric acid will affect your quartz crystals in the slightest. If you see any fizziness at all with hydrochloric acid, it just means you had a bit of calcite coating on the crystal (it would be whitish) that is dissolving in the acid.
Nope. Quartz is tough stuff.
I forgot to mention that after you clean your rocks, you should let them soak overnight in a baking soda solution. It’s really annoying when acid leaks out of some little crevice, and wrecks the finish on your bookcase. Baking soda will neutralize the acid, and prevent that problem.
Great. I’ll soak it in this stuff overnight and see what happens, and then look for some baking soda or some other alkaloid. Thanks.
Just updating you guys. The Zap! didn’t do a very good job. So yesterday I went to the hardware store and bought some 31.5% hydrochloric acid. This stuff is intense. It certainly cleaned the outside of the quartz, but unfortunately there’s some yellow crap inside it which is unreachable. At least it looks significantly better.
For anyone else trying this, I used baking soda to neutralize the acid before disposing of it. (I haven’t disposed of it yet actually.) It’s an endothermic reaction, meaning the solution got cold, not hot, but it needs to be added slowly or the acid will bubble over which isn’t good. Then you should have a solution of saltwater and a little excess baking soda. I’m going to start a new thread about what I can do with the rest of the acid.
Could it be that you have a pale citrine then?
I don’t think so. It looks more like milky quartz. It just has impurities of iron or sulphur I guess. I’ve tried to take pictures but my digital camera won’t focus at that close.
(It’s disappointing to find that I’ve found the most common varient of the most common mineral, but I guess that’s how it goes.)
If that is so, then:
Bolding mine.
Maybe not as common as you thought at first. 
Heh. Well I guess it fits the definition for citrine more closely, but it looks far more like the picture of milky quartz. I don’t know. It didn’t come out as clean-looking as I had hoped for. It has got me interested though so maybe I’ll find something better.
Can you post a picture? What were you hoping to use them for? Why can’t they be part of a more natural display of minerals? 
Maybe you’ll find some nicer quartz in the same area? I think it’s neat that you found some crystals in the first place, there’s a decent chance you’ll spot some more now that you’re looking too. I’m rather fond of quartz crystals, I found a rather large clear one (with a cool bubble) as a child.
I tried to take some pictures but my camera won’t focus that close. I just wanted them because they look cool. I’ll keep looking for cleaner looking ones.