1.4 Why are there so many names?

There are more than 100 igneous rock names defined and used in the Rock Library of this website. Why are there so many names? Couldn't geologists get by with only a few? Yes, but although the many rock names seem daunting to new geologists, rock names actually save time and improve communication. When a geologist uses the name "granite" in a research paper, the reader knows that the rock is a coarse-grained igneous rock consisting predominantly of alkali feldspar, plagioclase feldspar, and quartz, with less than 10 volume (modal) percent mafic minerals, with plagioclase being at least 10 volume percent and less than 65 volume percent of the feldspar minerals, and with quartz being 20 volume percent or more of the felsic minerals. One word, "granite," can be used instead of the more than fifty words in the definition.

Because of the convenience of using rock names, geologists have coined many rock names for the rocks they were studying. Some are old names, commonly based on appearance, such as "granite", from Latin granum meaning grain and referring to the visible crystals in the rock. Others are based on the predominance of a mineral, such as "anorthosite" and "pyroxenite" referring to the high plagioclase (anorthite) or pyroxene content, respectively. And some are based on places that the rock type was first observed, such as "andesite" (Andes Mountains) and "norite" (Norway). The original meanings for the names can be obscure, but once you have seen or studied a particular rock type, its name will have a meaning for you. ("The one who sees the most rocks wins!")

If you want to try your etymological skills with rock names, click here
Name Challenge