|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).