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| A HAND-MADE SPHERE OF GONIOBASIS IN MICROCRYSTALLINE QUARTZ FROM THE GREEN RIVER FORMATION, SOUTHWESTERN WYOMING. THE TWO "BRIGHT" SPOTS ARE REFLECTIONS FROM THE LIGHT SOURCE. THE WIDTH OF THE SPHERE IS ~8.75 CM. |
At the recent AFMS show in Minnesota, I noticed a number
of specimens labeled “Turritella Agate” that were offered for sale. I always sort of flinch when I see that term
since the specimens are not agate (in the true sense of agate being banded or
included), and second, the fossils contained are not the gastropod (snail)
genus Turritella ( a marine form). But, I have come to sort of accept the term since
the name “turritella agate” is well entrenched in the rock and mineral
literature, and certainly specimens are sold as such in hundreds of rock shops
and shows.
The “turritella agates” at the AFMS show were
collected from southwestern Wyoming in the Green River Basin at a locality
termed the Delaney Rim. The Green River
Basin was the site of a large freshwater lake during the Eocene Period of the
Tertiary (34 my—60 my) termed Lake Gosiute, a body of water that teamed with
life—including millions of high-spired snails of the genus Goniobasis or Elimia.
It appears that the term “turritella agate” is here
to stay in the rock and mineral trade.
However, savvy rock hounds will know that the snail is not Turritella and that the mineral is
really not a banded agate (but is a microcrystalline quartz). Whatever the case, a
nice polished specimen is a wonderful addition to any collection. I acquired my sphere from a close friend in
Salt Lake City, Jim Madsen (now deceased).