Some 9 years ago I was hired by Boise Cascade Corporation to evaluate
the opal deposits on their Louisiana forest land. I had had the
opportunity to inspect some of the rough and processed material being
offered about the same time at the Pueblo Inn at Tucson. Geologically
or perhaps mineralogically speaking the material is a “common
opal-precious opal cemented, lithic, fossiliferous, arkose” or
perhaps simpler a “dirty opalized sandstone”. While the bulk of the
material that I inspected at that time was as described above, there
was one piece that emerged from one of the local Louisiana diggers
that was +/- 80 grams of pure, transparent, colorless (and
unfortunately without fire) opal. According to the miner it had been
out of the ground “fer yeears” and showed no sign of crazing.
The macro geologic literature that covered the area indicated that
the systems source was a volcanic or large scale hydrothermal system
in what is now Texas. While I have neither samples nor a copy of the
Boise Cascade report (it was proprietary) I do remember concluding
that what value the bulk of the material had was low (less the
USD$20/kg) and had utility for carvings, eggs, spheres and large scale
slabs, I do distinctly remember mentioning that if material similar to
the large single “bomber” I was shown but containing precious opal
fire was discovered, then Louisiana would quickly occupy a spot as a
important locality. There were stratigraphic considerations that made
exploration difficult and mining, the strata that contained the opal
and “opalized sandstone” occupied a topographic “low” in the region
just at water table, making any mining effort expensive, primarily
from the enormous pumping costs which were not warranted by overall
low value of the material. In fact the primary miner of the material
at that time was limited to active mining during the dry, end of
summer and fall months into early winter when the water table was at
its lowest. The primary pit at that time was adjacent to a flowing
stream.
In conclusion while I think the material was very interesting I
perceived it at that time to be more of a geologic or mineralogical
oddity then a commercially viable gemstone. However there is a great
deal that could have changed in the ensuing 9 years.