Cleaning large amethyst cathedral geode

I have a pretty decent-sized amethyst cathedral geode similar to
this => http://www.ganoksin.com/gnkurl/ep7z3m

I’m moving to a new studio space and would like to keep it either
there or in my office but, it needs a little bit of cleaning up
first.

Because we kept the geode in the shower in one of our bathrooms,
there is a slight build-up of mineral and soap deposits on the
crystals. We have hard water, but we do have a system-wide water
softener installed, so the deposits aren’t TOO bad. There’s still
enough of a visible layer of deposits that it cuts down on the
geode’s sparkliness (word?).

I was thinking maybe soak it in a 1:1 solution of vinegar/water–or
perhaps even just straight vinegar–for a couple to a few hours,
then scrub with a toothbrush (or small brass bristle brush) to see
what happens? Speaking of cleaning with a brush, those freaking
crystals are sharp! ;-D --So I’d like to avoid having to get my hands
inside of it–I’ve stabbed myself a few times already despite trying
to move carefully. That is to say, a mineral-dissolving soak of some
kind would be preferred. [I wouldn’t dare think of using something like CLR on it–or, maybe that would work?]

So, any other thoughts on how to clean one of these? I guess my
concern is not knowing how susceptible the coloring of the amethyst
is to any kind of (harsh) cleaners. The crystals are a really deep,
pretty purple, and I’d like for them to remain that way.

Thanks in advance.
Tamra Gentry

amethyst cathedral geode CLR should be safe, but if vinegar will
work, I'd use that - safe and cheap. 

Quartz from Arkansas mines is often cleaned with hot oxalic acid,
but that shouldn’t be needed for water deposits.

Al Balmer
Pine City, NY

Thanks for the info, Al. (Maybe soaking it in a bath of steamed
spinach might do the trick? ;-D)

Seriously though, thanks. I didn’t know about oxalic acid–both with
regard to that, and with regard to its content in certain foods
(o.0). Going to do more research on the food component, out of
curiosity…

Tamra