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