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Orange Peel on Ruby-Zoisite Cab


#1

Good Day All

I purchased a large ruby-zoisite crystal carbuncle a few years back
and have just got around to cutting cabs out of a slice of it. Just
purchased the equipment to cut and cab it. So to say the least I am
new to the cabbing field. Probably not the easiest material to start
with. The ruby part is about 88mm wide, the zoisite outer layer is
about 22mm and the whole is about 130mm long and it weights 8 pounds.
Looks like someone cut the top off a stalactite so it’s triangular.

I have cut two cabs out of it. The first is half ruby, half zoisite.
I
have search on orchid and there is a post from few years back talking
about Ruby Zoisite but it deals with trouble polishing the zoisite.
That doesn’t seem to be a problem for me. Zoisite polished well.

I worked the first in a classic oval through, 260, 600, 1200, 3000,
14000, 50000 diamond grit. The 260 through 3000 on Doug Klein’s
Eastwind Lapidary Diamond 8 inch flat lap diamond disks. (These disks
are awesome)

The 14000, 50000 on a flat lap made from sanded plywood with diamond
oil paste.

I had some chipping on the roughing out on the 260 with the first
one, but it cleared up nicely on the 600.

I worked slow and easy and took my time. It came out fantastic. The
zoisite and ruby polished up to look like waterglass. Total Bling.
The ruby has shimmer and stars showing all over it when in the sun
and you move it through its curve. It also appears to have a totally
clear section running through it 10mm wide.

The second one was cut from the same piece right ontop each other so
they are sisters. This one just doesn’t have the zoisite. I cut it
off.

It chipped on the roughing on the 260 and kept chipping and pitting
from there.This cab is cut to the shape of a claw or fang, long and
narrow. All this pitting and chipping confused me because the first
one came out so well.

I have studied the mother crystal and it looks like the 6 pie
sections of the ruby have a very obvious grain to it. The first cab
was cut with the grain and the second against the grain.

I have search the web looking for answerers to my chipping problem.
No luck. I am a member of a lapidary club and the consensus is that I
either cover the ruby in epoxy to hide the chips and pits or just
live with it because that is the nature of the material. I have also
been told to polish it on a copper plate using diamond. This from the
faceters in the club.

That doesn’t work of me. I have looked at other ruby-zoisite cabs on
the web and most appear pitted in some form but not all, some are as
smooth and shiny as my first one.

I know Orchid is mainly a metals-jewelry form, but I was hopping
there is someone out there with experience dealing with this type of
issue.

I think it has to do with the direction of the cut versus the
direction of the grain.But what do I know, I am new to all this and
those are my observations.I am not willing to continue cutting it
till I have an informed direction, or at least a hint of what might
be happening with this second cab and it pits and chips.

Oh ya one more thing I took a slice off the tip to look at the
mother from top and bottom and there is a totally red clear crystal
rod that is about 10mm wide running right through the middle of the
mother. It is transparent as far as I can tell. I shot a lazar though
it and it shined out the other end and the two cabs have a portion of
this crystal attached to it and it’s clear. Should I try and isolate
this area as something special?


#2

Isolate definitely…!

try leaving a margin of zoisite all around the cylinder…cleavage
seems to be your disadvantage from what you described…the ruby in
zoisite is more akin to a tourmaline crystal…and i completley agree
with the copper and diamond lap recommendation.slow speed,cool as is
possible cutting, and skip the 250 for something closer to 400 to
start or look at some 3M products that have aggressive cutting
capabilities with a webbed matrix of ceramic and diamond or ceramic
and silicon carbide or zirconium…you can also just use a diamond
wheel on a flexshaft ( continuous rimmed) at no more than 3500 to
rough out your shape if its well lubricated with wintergreen oil,or
synthetic methyl salicylate, or a product like liquid bur-lube to
eliminate chipping,( reduce speed if you get any chatter)…I watched
a guy at a “granite counter top " place cut a slab of it,followed by
a slab of labradorite last Saturday…(by slab I mean 64"x 98” pieces)
he had little chipping with a 60 inch saw blade he prepped with
diamond spray and kept it wet and cool…the finished pieces were
glass like with his copper and diamond polishing lap though he said
he can get away with a polish like Linde A or cerium oxide on the
ruby and zoisite…

a great reference is the international facetter’s guild’s
archives…or the eclectic lapidary

R.E.Rourke


#3

A clear rod thru the middle??? Red flags to me! Sounds like the ruby
was grown by man - not Mother Nature in vugs.

Judy Shaw


#4

I would say you are right about the chipping and dullness being due
to the orientation of the crystal. I have suffered from this when
polishing star sapphires. You can minimise the damage by grinding
and polishing on a loose diamond paste, IE: use a suitable cloth to
carry the abrasive rather than a hard lap which causes the diamond to
embed in its surface and behave as a fixed abrasive. A short nap
cloth such as silk should work well. It will take longer to do but
with a stone as you describe it will be worth while. It may not be
perfect though if you are only a few degrees from the cleavage plane
you may still get problems.

nick


#5

Hi Folks,

I missed the original posting on this topic, so I don’t know how
large the cabochon in question is, but if it’s less than about 4" in
diameter, an easy solution is to use Hi Tech Diamond Products’ 6"
smoothing discs (which are resin-bonded fabric discs) atop a 6" flat
lap, at slow speeds (i.e. less than 700rpm). As I’ve recently posted
to another list, I’ve used these with great success on a wide range
of materials, and have used their synthetic leather polishing pads
with equally excellent results. (I’m not connected with them in any
way, FWIW.)

Thedre are two recommendations I’d like to add to the above. First,
steer clear from their (and other mfgr’s’) synthetic canvas
polishing pads, at they don’t seem to either hang onto the polishing
compounds or deliver as even a finish surface as well as the syn.
leather (which has a finish approximately midway between split
cowhide/suede and felt). The second is to place a layer of padding
between the lap and the polishing surface, before you turn the arbor
on. I’ve found that a self-cut piece of that neoprene foam-inundated
nylon netting (that’s sold for everything from tabletop placemats
and throw rug skid-resistors to shop machinery anti-vibration pads,
nowadays) works wonders, as it forces the polishing pad to conform
to the nuances of your cab’s surface, regardless of its contours.
Also, pay attention to the demarkation line between the corundum and
the zoisite, and try to have the directional grain of the oncoming
wheel approach it from a diagonal perspective, rather than head-on.
This may help reduce some of the undercutting, as well.

Douglas Turet, G.J.,
Turet Design, LLC
P.O. Box 242
Avon, MA 02322-0242
Tel: (508) 586-5690
Fax: (508) 586-5677
turetdesign.com