Gemstones & Pearls: Gemology
When Fool's Gold Marries Quartz
Bound Together for Eternity
Pyrite and quartz are often perfect companions. A smattering
of pyrite crystals sprinkled generously through quartz often
lends a subtle but entrancing metallic glitter.
When a skilled cutter positions the lustrous inclusions of
pyrite so you can see the crystal faces with the naked eye, the
gem can become a collector's item. You can stock gems like these
as a curiosity and a sales tool to show customers the wonders
of gem formation.
Here are some gemological details that may interest your more
A basic question is whether this pyrite-in-quartz gem is more
correctly called pyrite or quartz. There are arguments in favor
of pyrite. "There is more inclusion than gem," says
Simon Watt of Mayer & Watt, Maysville, KY, who owns the gem.
The profile view illustrates the point, and a specific gravity
test indicates the gem is much heavier than quartz. However,
refractive index indicates quartz.
Another gemological factor to consider is when the pyrite
forms. "Pyrite often forms its own birth-chambers,"
says The Photoatlas of Inclusions in Gemstones (E.J. Gübelin
and J.I. Koivula, ABC Edition, Switzerland). This suggests the
pyrite inclusion forms at the same time as its host mineral,
which makes it a syngenetic inclusion. Conversely, epigenetic
inclusions form after the development of the host crystal.
In addition, the pyrite in this example clearly shows a typical
step-like growth pattern on the surface of its crystal faces.
A few spots along the division between quartz and pyrite show
spectral interference colors areas of stress created by
the growth rates of the different minerals. Aside from these
rather minor flares of color, the marriage of this quartz and
pyrite seems permanent.
- Mayer & Watt, Maysville, KY; (800) 344-4110.
by Robert Weldon, G.G.
||Front view of the pyrite-in-quartz gemstone.
|Profile view of the pyrite-in-quartz gemstone.
Gem courtesy of Mayer & Watt, Maysville, KY.
Copyright © 1999 by Bond Communications.