Drilling fossils

Hi Orchid! I have a commissioned piece I’m working on that has a
marine life fossil,2.5" spiral shell fossil, the customers, and I am
wanting advise on drilling a fossil. The plan is to drill a small 2mm
-3mm hole through the fossil for tube insertion. The hole would run
width wise not length.I am assuming the fossil is a limestone, for
lack of a better description. I do have proper drills for regular
stone drilling and have done many successfully, just haven’t done any
fossil material yet. Do you think this will drill clean or crumble?
Any suggestion or comments would be greatly appreciated. Nancy


Without being able to examine the piece it is difficult to say how
well it will drill. At the Gem and Mineral Society, we are called
upon periodically by our affiliate museum to drill or cut a piece of
fossilized material. Sometimes it works well…sometimes it doesn’t.
If you can determine the piece is solid, a diamond drill should go
through pretty well. Sometimes, these items are pretty brittle
though and chipping or cracking is not uncommon. Furthermore, it
could be incomplete in metamorphis and the center might be
soft…making it even more delicate. Guess its a crap shoot unless
you can get a good idea whats inside.

Not much help I’m afraid but best I can do without seeing it.
Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry! @coralnut1

G’day Nancy et al; If you want to check whether the fossil matrix
is limestone or not, simply place a single drop of acid on a place
that won’t notice much and observe it through a magnifier. It will
only bubble if it is limestone or contains a carbonate.

Any acid will do even vinegar or fresh pickle. The only other
material could be silica and that won’t bubble. Take care with the
drilling; you’ll use a diamond drill with the job covered by water of
course, and you will raise and lower the drill very frequently. I
suggest that you should use a cone or ball burr to gently flare the
hole on both sides, then flare flare one end of the insertion tube
of such a length that it protrudes about one or two millimetres., set
it in with a good epoxy resin, then when hardened, flare the other
end of the tube. The flaring is extra work but will pay off as it
will avoid excessive wear on the holding ring or cord.

Cheers for now, John Burgess; @John_Burgess2 of Mapua, Nelson NZ

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Don and John, Thank you for your response. After testing the fossil
with acid(vintager) as you suggested, The fossil proved to be
limestone. I proceeded to drill slowly holding my breath…I’m glad it
was fairly soft material… it drilled out fast then I could breathe!
The tube inserted perfectly , I used the idea of epoxy in the hole
for stablizing the tube to flare second end easily. The completed
piece turned out just as planned! Small victories, big confidence
boost. Thanks Orchid. Nancy