What is llanite crystal?

Llanite is a rare and unusual type of igneous rock that is found in Central Texas, primarily in the Llano Uplift region. It is composed of blue-gray microcrystalline quartz, feldspar, and biotite. The feldspar in llanite is irregular in shape, giving the rock its characteristic speckled appearance.

Llanite is interesting to geologists and collectors because it contains plagioclase and microcline feldspar crystals that are often twinned. The crystals are small, usually less than 1 mm in size, but they can be easily seen with the naked eye. Llanite is also known for its unique blue-gray color, which comes from the quartz and feldspar in the rock.

The origin of llanite is argued among geologists, but most agree that it is a rare type of rhyolite. It is thought to have formed when magma from deep within the Earth intruded into existing granitic rock and crystallized very slowly, allowing time for the feldspar crystals to grow. Llanite is considered to be a very old rock, dating back to the Precambrian era, over a billion years ago.

In addition to being a beautiful rock for collectors, llanite has also been used as a building stone in many historic buildings in Texas, including the Texas Capitol Building and the University of Texas at Austin.