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Working With Larimar

#1

To everyone, both on and off-line, who responded to my request for
words of wisdom concerning Larimar, my heart felt thanks. Like one
who told of his experience with Larimar, the entire piece that I was
working with turned out totally unusable. The cost was borne by my
client, because he was the one who purchased it in the Dominican
Republic, but that doesn’t make it any less painfull. Not only did
he suffer monetary loss, but I wasn’t able to make anything for him.
After this experience with Larimar, I would never take another
commision to make anything with it, there are too many other
beautiful stones to use.The one consolation? I don’t feel so
incompetent now, thanks to several of you.

Best wishes,
John Barton

#2

All,

Cutting Larimar is quite a chore. About 10 years ago in Tucson slabs
of Larimar started to appear for sale. Not knowing the material make
up I started cutting it as I would any soft lapidary material. A huge
pile of junk resulted. Research into the make up of Larimar resulted
in hints as to why the material was so fragile. Larimar is a
pectolite. A pectolite is a mineral that forms in sheaths. These
sheaths resmble sprays like in sagenites, but are not encased in
silica bearing minerals. Sheaths are held together by very weak
chemical and mechanical bonds.

Once I knew this I started to experiment with different cutting
methods and holding methods. First of all I have found out by
working with other soft and fragile materials that mechanical shock
wave can shatter the bonds in the material and cause destruction,
kunzite has similar cutting problems to Larimar for different
reasons. Diamond, hard bonded wheels create mechanical shock through
the stone and rapidly cause destruction of the bonds which hold the
material together. Diamond belts on a rubber expandable wheel do not
cause near as much destruction. 320 grit or 600 grit silicon dioxide
belts on rubber expanable drums cause even less destruction. I saw
Larimar with a 3000 rpm diamond saw and a .012 kerf, 4 inch blade. I
saw well away from my desired shape and rough grind on a new 320
grit silicon carbide belt. Dopping is accomplished using super glue
and acetone to release the bond. Finishing is accomplished using
rubber backed pads impregnated with diamond and mineral oil for
lubrication. Using this process I end up with less than 10% breakage.
Some stones still defy processing. Larimar is incredibly beautiful,
but very fragile.

Gerry Galarneau
gggemswcr@cox.net
www.galarneausgems.com

#3

Gerry; great on your experience with Larimar. I wish
that I had the info first time around, I would have tried the
expandable drum approach. In the finishing polishing process, what
other options work well with Larimar besides diamond with mineral
oil? Also, are the pads leather with the rubber backing?

John Barton

#4

All & John,

Pads are obtained from Johnsons’s Brothers and called compound
discs. They are supplied with a PSA (Pressure Sensitive Attachment)
backing. I use aluminum discs(spin discs) that are attached to an
end shaft via a shaft adapter. Spin Discs have a standard screw in
the center of the back of the disc. On the aluminum disc attach a
1/4 inch rubber lapidary disc. Attach the compound disc to the
rubber. I charge the compound disc with syringed diamond compund.
Motors of 1/4 hp, 1725 rpms are used to power the disc. In my shop I
have three motors set up with three differnt grits of diamond. Using
this system I very seldom use a stone that has survived the
preforming stage.

Gerry Galarneau
gggemswcr@cox.net
www.galarneausgems.com