TINY, GEMMY, TERMINATED BARITE CRYSTALS PERCHED ON MASSIVE BROWN CALCITE AND PARTIAL, NERLY CLEAR CALCITE CRYSTALS. HEIGHT OF SPECIMEN ~3 CM.
The Book Cliffs are one of the most recognizable landforms in western Colorado and eastern Utah . For about 200 miles this escarpment extends from where the Colorado River descends south through DeBeque to Price Canyon near Price, Utah. The lower slope exposes marine shales of the Cretaceous Mancos Shale while interfingering sandstone beds of the upper Mancos and overlying Mount Garfield Formation (generally referred to as the Mesa Verde Group or Formation) were deposited in fluvial (stream), swamp, flood plain, and near shore marine environments. The sandstone units capping the cliffs are fractured with vertical joints that reminded some long forgotten person of a row of books. In the area of economic geology, the Book Cliffs contain important reserves of coal. Positioned on top of the sandstone, but usually situated back from the edge, are various early Tertiary rock units, for example the Green River Formation and the DeBeque Formation.
|BOOK CLIFFS NEAR GRAND JUNCTION, COLORADO.|
|BROKEN CONCRETION IN MANCOS SHOWING WEATHERING BACULITE CEPHALOPOD.|
It was not long before it became apparent that perhaps I was not the first collector to bang on the rocks—most concretions were cracked and broken! So, I checked my water supply and headed up the slope and away from the roads, still banging on the rocks. The first thing that I noticed was that some of these rusty colored concretions were “really large", like 6-7 feet in diameter. The second obvious item was the large number of straight-shelled ammonites, Baculites sps. weathering out of the concretions. I collected a few and noticed that most were steinkerns, or internal molds, and they did not exhibit remnants of the external shell. However, some of the specimens displayed nice suture lines.
The first crystals that I found were pieces of calcite, then lots of calcite! But, I was looking for the spectacular water-clear crystals of barite, and they soon appeared. These specimens are beautiful, usually prismatic, nicely terminated, gemmy, and water clear; however, some crystals with a yellow tint have been reported. The ones that I collected were small, mostly less than 3 cm., but “nice”.
GEMMY, TERMINATED, WATER CLEAR BARITE CRYSTALS; HEIGHT OF SPECIMEN ~2.2 CM.
It is my understanding that the crystals have been collected for decades, but are still available for those collectors willing to take a little hike and bang on the rocks.
HEIGHT OF CRYSTAL ~2.2 CM.