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Cabochons for rings


#1

I would love to see opinions about what cabochons can be used in
rings and which to avoid. I can find out Moh’s hardness of stones
but I don’t know where to get info on toughness of materials. I have
seen recommendations to stay above Moh’s 7 for rings, but that sure
limits the options. Also, opals and turquoise, etc. are used for
rings. What about labradorite?..Chalcedony okay? Others?

J. S. Ellington
jsellington@cs.com


#2

J.S. - For rings with “exposed” stones I usually stay with harder
materials, meaning agates, jaspers and jade. These materials are
less apt to fracture, and they have no cleavage. Opal is too soft
for good, everyday rings (commercial jewelers make a mint on
replacement opals, and some folks go through many in their favorite
rings), and none of the feldspars (including labradorite) are good
due to perfect cleavage and low resistance to abrasion. For
"cocktail" jewelry, rings worn only for special occasions, you may
use anything except the softest or most cleavable stones. I
occasionally succumb to making basket-work rings with opals and
other less durable stones, and I tell my customers that these rings
are only for flaunting, and ought to be removed for even washing
dishes, and never worn in an office or yardwork setting.

Jim Small
Small Wonders Lapidary


#3

JS, When people say, “Stay above Moh’s 7 for rings” they are in my
opinion generalizing. If you check your stones, you will find albite
jadeite runs 6 to 7 while actinolite nephrite from 5 to 6.5! Even
jasper/agate/chalcedony/flint/chert runs from 6.5 to 7. The jadeite
and nepherite are usually very tough due to their structure. Jasper
can be tough depending on the impurities contained, while chalcedony
and agate tend to be brittle and sometimes down right pithy. Under
heavy wear or over time, all of them will scratch, loose their polish
or even crack, even jadite. For all that matter, I have seen many a
sapphire or ruby on which the facets are all scratched and the meets
rounded and dull and they are a 9!

To learn about these different characteristics, you have to both
study the scientific characteristics and, as these characteristics
are also generalizations, cut the stones in their many different
forms. Only then will you have a true appreciation for a stones
durability.

There are things that can be done mechanically to protect some of
the softer stones such as use large prongs, high bezels, add
embellishments along the top of the stone, use shadow box settings,
etc. Soft stones should always be set in a strong and perfectly
formed bearing lest they be twisted during wear causing them to
crack. I have spent many hours replacing the bearings and opals in
poorly made SE Asia settings. Same for turquoise.

Lapis lazuli, malachite, various feldspars, tanzanite (not durable
at all), the list goes on and on of the most beautifully colored
stones that probably should not be mounted in rings but not to do so
is to deny their beauty if not their durability. When you do set and
sell a piece of jewelry with one of these stones, educate the
customer how to care for them. Is this a ring to flaunt or lay brick
with? Aye, thats the point.

Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry! @coralnut2


#4

Dear J.S. One of the beauties of silver and cab rings and/or other
jewelry is that you can be less inhibited about what to use as cabs.
So what if the cab gets scratched down the road. Peeling back the
bezel is no big deal and popping in another cab is also fairly easy.
I regularly do this and you would be surprised how easy it is to use
a foredom to shape an irregular cab. I use a mizzy wheel to do the
rough shaping and then use pop off sanding disks to do the finer
sanding. On harder materials it is easy to prepolish the stone using
a one inch strip of 600 grit carborundum sandpaper. I mount the
stone on a sixteen penny nail using five minute epoxy and then place
the dopped piece in a bench vise with the stone facing up. I then
use the sanding strip to remove the “flats” from the stone using a
"shoe shine" type stroke. The final polish can be achieved on a
jewelers buffing wheel. You may have to refer to a lapidary manual
to find the right polishing compound for a given stone. However, Zam
usually does an adequate job if you have done a thorough prepolish
sanding. It is easy to over-react to inhibitions about stone softness
and/or toughness. After all, Turquoise, pearl, amber, coral,
variscite and many other stones have been used in jewelry over the
millenia and, while they don’t hold up as well as harder stones,
they do give adequate service and it is usually no big deal to
either replace or repolish them.Ron at Mills Gem, Los Osos, Ca.


#5

Dear JS, I have to agree with Don about deciding which gemstones
should or shouldn’t be used in settings that might be detrimental to
the stone, such as rings, bracelets, etc.; you really do need to
study their characteristics because there are other considerations
besides hardness and toughness that matter here, especially cleavage
planes. As an example, diamonds are recognized to be the hardest
natural gemstone, everybody knows that. We use it every day to cut
our rocks and gems, along with other, softer abrasives. It will
slice through jade like nobody’s business. Yet, anybody can use
diamond abrasives to fashion a hammer from a block of jade, then
turn around and smash a diamond to bits with that same jade hammer.
The lesson here is that, while hardness is a weighty factor in
choosing a setting for a stone, things like toughness, crystal
structure, crystal habit and formation are also factors.

Don also mentions educating the customer. This is an absolute MUST.
Another example: the general public thinks that diamonds are
completely indestructible, when in reality, they can be damaged very
easily. In GIA’s Diamond Grading Class, I saw dozens of diamonds
with rounded facet junctions, pits, scratches, cavities, nicks, etc.
Definitely ask if "Is this a ring to flaunt or lay back with?"
Jewelry consumers assume that, if it’s a ring, it was made to be
worn ALL the time, even that opal ring, when they’re doing the floor
with Mr. Clean (ammonia isn’t recommended for opals). Also, many
gemstones cannot be cleaned with solvents such as commercial jewelry
cleaners, ultrasonics or steam.

The upshot of what I’m trying to say is, you may mount practically
anything in a ring, including opals, turquoise, lapis, etc., and
it’s anybody’s choice. But, as Ron said, “So what if the cab gets
scratched down the road”. As long as the customer knows the
limitations of their jewelry regarding DURABILITY is concerned, and
as long as you can provide the service they’re likely to eventually
need (repolishing, replacement, etc.) then, feel free.

Cheers from James Who Has No Studio in SOFL where found jewelry IS a
stippled elephant