I have a Rhodocrosite stalagtite, and cut a few slices off of it.
I’m trying to do a final polish , but all I get is a medium glaze.
I’m using Cerium Oxide on Leather. Its an 8" split cowhide piece and
I’m using the split/rough side, just a fingertip of Cerium powder,
lots of water. It looks like all the polish marks are gone, but it
just dosent have that ‘like glass’ look. Any ideas would be
appreciated.
Love and God Bless
-randy
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I haven’t worked with Rhodochrosite, however, I believe that it is
basically pink calcite. as such, you may be able to get a good polish
by adding a bit of acid to your cerium oxide slurry. You may even be
able to polish by dipping the cab in acid. I understand that this is
how those Mexican onyx carvings are polished- acid dip, rather than
abrasion.
I do real well with Zam on my buffer. I use one of Rio’s yellow
tightly stitched 6" buffing wheels. Rhodocrosite will pit if it gets
too hot. Also, wear a mask as I believe the stone contains
strychanine (bitter almonds smell).
In “Gem Cutting” by John Sinkankas he says that the perfect cleavage
that rhodochrosite has will tend to give small, deep angular pits
during grinding. Grind only on fine wheels. He recommends prolonged
fine sanding, wet, or diamond on wood with 15, 6, and 3 micron diamond
on wood. then a fine polish with tin oxide or Linde A on leather or
wood, or 1 to 1/2 micron diamond on wood.
It requires a light touch on the final finish… I find tin oxide to
work best.
usually you can go from 600 to finish on the leather… I use soft
elk hide for finishing… also a slow wheel for the final polish makes
a huge difference… I have a separate 300rpm wheel on my flat lap
just for the final polishing…
You can see some finished pieces of rhodochrosite on my site at:
Soft minerals are a near challenge… the Ruby in zoisite on my site
has take some real experiments to get a high polish on such disparate
minerals… from 6 mohs to 9 mohs for the ruby…but worth the
effort big time :>)
Enjoy your journey!
all the best to the finest online group anywhere.
monk
Source for gem stones, crystals, jewelry
Metaphysical, New Age, Contemporary
Hello Randy, The problem may be porosity. Some of the stalactite
formations just have to many pits and openings. If you can afford to go
one step higher try tin oxide on a rock hard felt wheel. Just watch
out for heat build up. Make a slurry of tin oxide and water and apply
with a cloth. Make sure the wheel is very wet. You can use tin on
leather too. Steve Ramsdell
Just wanted to add a couple of things to the ongoing discussion
concerning polishing difficult materials. I would strongly discourage
using any kind of an acid wash with your Rhodocrosite. The reason
being is that the material is made up largely of calcium carbonate
which acts as a base (In an acid/base reaction) whenever you put the
rhodo. in an acid it will start to dissolve you will get a little
white precipitate (formerly part of your Rhodo.) and some carbon
dioxide gas bubbling out (as the other part of your Rhodo.). I don’t
see how this could possibly help out in polishing the material.
For all of my cabbing material I have switched to 14,000 diamond
before a final polish with tin, cerium etc. or I will use 50,000
diamond paper that I got some time ago in a roll of 1-1/4" wide "film"
material, use like a worry stone when you go on those necessary
errands. I get excellent results on Ruby/Zoisite with these methods.
I found on Ruby/Zoisite that tin oxide will polish out the Zoisite and
the diamond will do the Ruby and not harm the polish on the Zoisite.
Just wanted to add a couple of things to the ongoing discussion
concerning polishing difficult materials. I would strongly discourage
using any kind of an acid wash with your Rhodocrosite. The reason
being is that the material is made up largely of calcium carbonate
which acts as a base (In an acid/base reaction) whenever you put the
rhodo. in an acid it will start to dissolve you will get a little white
precipitate (formerly part of your Rhodo.) and some carbon dioxide gas
bubbling out (as the other part of your Rhodo.). I don’t see how this
could possibly help out in polishing the material. For all of my
cabbing material I have switched to 14,000 diamond before a final
polish with tin, cerium etc. or I will use 50,000 diamond paper that I
got some time ago in a roll of 1-1/4" wide “film” material, use like a
worry stone when you go on those necessary errands. I get excellent
results on Ruby/Zoisite with these methods. I found on Ruby/Zoisite
that tin oxide will polish out the Zoisite and the diamond will do the
Ruby and not harm the polish on the Zoisite.
See LAPIDARY JOURNAL INDEX . They have a nice article about how to
polish Rhodochrosite. It was 1997 I think. By the way are you talking
about Rhodochrosites Crystals for facet or Rhodochrosite from
Argentine for Cabs mostly? Regards
Randy, use ZAM on leather. Polishing starts when leather starts to
"grab" the stone. At this point lighten up the pressure to avoid both
orange peel and over heating. Will E.
I concur with Will. Zam works great with Rhodocrosite. Keep it wet
with a light touch! I went from 14,000 micron/grit to Zam. I cut a lot
of this material when I was an apprentice and I still like it even
today. Have fun! Galen
