New Origin I.D. method for emeralds

The December issue of “Science News” (vol. 164, p. 371) reports a
method for pin pointing the mine that an emerald came from. A
previous procedure utilizing the ratio of oxygen isotopes to
identify the origin of an emerald has proved unreliable because
emeralds from Russia, Pakistan and Madagascar often have the same
oxygen isotope ratio.

The new method determines the ratio of hydrogen to deuterium of
water that is in extremely small channels that are throughout the
stone. The channels are so small they contain only one or two
molecules of water. The method so far has distinguished emeralds
from ten mines in seven countries. Why the amount of deuterium
varies from mine to mine is not clear.

The method uses the infrared spectrum of the emerald to determine
the ratio of hydrogen to deuterium of the entrapped water. Infrared
radiation is in the energy range that matches the energy that
produces movement of atoms with respect to each other in a molecule.
The movements in a water molecule include spring like oscillations
of hydrogen with respect to oxygen along the axis of the bond
between them, wagging of hydrogen with respect to the oxygen bonded
to it, etc. The difference in the infrared energy absorbed by the
wagging of a hydrogen atom versus the wagging of a deuterium atom
would be appreciable in that deuterium has twice the mass of a
hydrogen atom.

The impact on the emerald business would be considerable if the
testing is economically feasible and proves to be as reliable as
indicated. Is this report truly a new development, or is it an
improvement of previous work that is common knowledge among the
stone experts of this forum?

Captain Blood
"Marlinespike Seamanship in Precious Metals"