[Rockhounds] WAS Rockhounds Digest, Vol 64, Issue 28 NOW even headless removing gel.

[Axel Emmermann]

> Let me know if boiling water works. 

[Axel] The best way to go about the problem is to let the gel dry out
completely. Then a few taps with a knitting needle breaks the gel so it can
be rinsed away with tap water. I just tested (thank you Murphy) the ONE tube
that showed a bizarre detail:  Liesegang rings.
When you make minerals in gels you actually let the ions that form an
insoluble mineral migrate towards each other from either side of a U-shaped
test-tube. You just let the gel settle and then you put solutions of salts
on both the surfaces of the gel, one in each leg.  For example; sodium
carbonate and calcium chloride: The calcium ions and the carbonate ions then
travel through the water-channels of the gel and meet on a 'collision-front'
where the mineral calcite forms (if you do it right and you're lucky). The
process is very slow and crystals grow over weeks to months. If you were to
mix the two solutions without the gel, you would merely get a white
precipitate of calcium carbonate.
Sometimes, however, an for no apparent reason the ions seem to create
several of these fronts. Then cloudy rings appear throughout a part of the
tube at regular and equidistant intervals where tiny crystals form. Useless
but interesting... It's like the crystallization happens only on the crests
of a standing wave. 
The one tube I tested was the one with the Liesegang-rings of fluorite,
which I made from sodium fluoride and calcium chloride.
The rings of CaF2 solidified to a strong crust and were difficult to break.

Liesegang rings often occur in nature too.
This is one of iron-oxide in sandstone :
http://www.cst.cmich.edu/users/dietr1rv/mimetoliths/mim-44.jpg
Also the rings in agate are Liesegang rings.

An here's the phenomenon in a test tuba and a Petri dish.

My next experiment will be to try making Cerium doped calcite. The only
problem is that I can't do that without cerium. Anyone sitting on a stash of
soluble rare earth salts?

Cheers
Axel