Gneiss is also a durable choice for interior uses, and makes a fantastic countertop or tile. The minerals in gneiss do not etch when exposed to normal household acids like vinegar or citrus. It tends to be low in porosity, meaning it is not likely to stain, but there is some variability here, and some gneisses benefit from sealing.
There are two caveats when working with gneiss. One is that the linear grain in the stone can sometimes mean that the stone wants to split along those layers. This is not common, but worth considering if you have a large overhang. Try to minimize overhanging areas where the overhang is parallel with the natural grain of the stone.
Second, keep an eye out for large areas of mica minerals, which are readily identified by their glittery look. In gneiss, mica minerals tend to form their own layers, which are likely weaker areas than the surrounding feldspar and quartz. Some of the dark colored gneisses have large amounts of biotite mica. Learn more in the article about schist. Search for:. Tags art award winner bathroom bluestone building stone magazine carving case study cleaning color commercial cost countertop design education exterior fabrication feel good fireplace floor geology granite healing historical installation interior kitchen landscape limestone marble monument quarry quartz quartzite remnants residential restoration sandstone selecting soapstone sustainability technology trends veneer video wall.
About a month into my college career, my parents visited for a hike in the New England woods. I had recently settled on becoming a geology major, which was an outlandish choice in contrast to the long line of engineering majors in the family. My dad pointed to the nearest boulder along the trail. I like it. Seeing gneiss, gabbro , labradorite , diorite , and other types of rock marketed as "granite" disturbs many geologists.
However, this long-time practice of the dimension stone trade simplifies discussions with customers since not everyone knows the technical names of unusual igneous and metamorphic rocks.
The best way to learn about rocks is to have specimens available for testing and examination. Small rock and mineral specimens about one inch in size are usually adequate for student examination and identification. However, many rock units, identified as gneiss in the field, have bands that are thicker than one inch.
If samples of these rock units are broken into one-inch pieces, many of them will be too small to exhibit the banding features of gneiss. This will confuse many students and cause others to incorrectly identify the rock. Teachers can avoid these problems by collecting specimens that clearly display a banded structure. Teachers who purchase specimens must examine them carefully before they are presented to students. After students have learned to identify gneiss and many other rock types, presenting specimens of gneiss that do not exhibit banding can be a challenging way to have students: A consider possibilities that are not obvious, and, B realize that a single rock specimen may not adequately represent a rock unit.
Article by: Hobart M. Find Other Topics on Geology. Maps Volcanoes World Maps. What Is Gneiss? How Does Gneiss Form? Rock, Mineral and Fossil Collections. Hardness Picks. Flint, Chert, and Jasper. Gneiss displays distinct foliation , representing alternating layers composed of different minerals.
Because of the coarseness of the foliation, the layers are often sub-parallel, i. This website uses cookies to ensure you get the best experience on our website. If you continue browsing, we consider that you accept their use.
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