Hoover Point is a road cut where the highway from Marble Falls to Kingsland (FM 1431) passes over Backbone Ridge. It's easily the highest point on the highway and there is a scenic overlook on the side opposite the road cut. This overlook (of Lake LBJ and points west) makes a relatively safe place to pull off the road. Crossing the road here is dangerous, be careful or you are liable to end up as road pizza. After years of visiting this outcrop in the morning, I recently visited it in the afternoon. Much better lighting for looking at things.

The rocks that make up this hill are part of a fault-bounded block of Paleozoic rocks which are surrounded by Precambrian granite. Here at the top of the hill you can see the Morgan Creek Limestone and the Lion Mtn. Sandstone, both are Cambrian in age. The Welge Sandstone is sandwiched between these two units, but is not easy to identify from ground level (probably the yellowish layers above the green layers and below the slightly darker Morgan Creek). A little lower down the hill, you can see the Cap Mtn. Limestone, also Cambrian in age. The Cap and Lion Mtn. units are in the Riley Fm., the Morgan Creek and Welge are in the Wilberns Fm.

The Lion Mtn. Sandstone (green-colored unit) is interesting in that it isn't a sandstone made up of sand-sized pieces of quartz, it's a sandstone made up mostly of the sand-sized pieces of glauconite (geo-geek discussion at bottom). The outcrop also has white-colored carbonate lenses that are rich in pieces of phosphatic trilobite shells (although I've never heard of anyone finding a whole trilobite here). In some spots, cross-bedding can be seen in these lenses. Glauconitic sandstones are unusual, the Lion Mtn. is the only example I've ever seen.

I think the most spectacular thing about the outcrop are the many small faults that cut the rock layers. Most of the faults have normal motion, but some have oblique slip. Look for the places where fluid flow along fault planes has oxidized the green glauconite into a reddish crust.

About those sand-sized pieces of glauconite. To a geologist "sand" is strictly supposed to a size term for particles that makes up a rock. So there are olivine sands in Hawaii, glauconitic sands (as above), feldspar sand, garnet sand, calcite sand, etc. Since quartz is both common and resistant to erosion, it makes great sand. This has lead to the unfortunate assumption by some that all sand is quartz sand. Not so, most but not all. Most of the other sandstone units in the Llano Uplift (Hickory, Welge, etc.) are made up mostly of quartz sand although other kinds of sand grains are present as well.