The Llano Uplift Dig Site – topaz, schist, gneiss, mica, quartz, and granite

Finding public access rockhounding sites in Texas, that let you keep what you find is an ongoing challenge. Many rockhounds have started to save the GPS coordinates when they find some good stuff that they think others might be interested in.

Here are coordinates for the Llano Uplift area.

Llano River Public Access Entry Point, near downtown Llano:
lat=30.7503786438
lon=-98.6668755605

Llano.River.Bluffs.CommonsThe Llano River has an amazing variety of rocks – many are creek-worn but there are some decent size rocks on the banks. You can expect to find schist, gneiss, mica, quartz, and granite. The water at this point of entry was about ankle deep in most places and there are several large boulders you can rest on while you pick through the endless cache of river rocks.

A wide variety of minerals are found in the Llano Uplift.  Quartz, microcline feldspar, plagioclase, biotite, and hornblende amphibole are common constituents of granites and gneisses.  Garnet, muscovite, biotite, staurolite and other metamorphic minerals occur in schists produced through the metamorphism of clay mineral-rich sediments.  Tourmaline occurs in some schists in Llano county and in quartz veins in  the Town Mountain granite near Llano.  Serpentinite, an ultramafic rock composed of serpentine group minerals, occurs in the Coal Creek igneous complex.

One of the most interesting of the Llano Uplift minerals is topaz, the Texas state mineral).  Colorless to pale blue gemstone-quality topaz crystallized from fluorine-rich gases in Llano Uplift pegmatites.

Colorless Topaz from the Llano UpLift area of Texas

Colorless Topaz from the Llano Uplift area of Texas

This is a photograph of one of these colorless topazes found in the Llano Uplift. These coarse-grained pegmatites are the last vestiges of water-rich granitic magma.  Coarse-grained crystals of smoky quartz, microcline, beryl, scheelite, and cassiterite also occur with topaz in the pegmatites.

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