What Minerals Form Rocks?
The list of minerals that commonly form rocks is short. Study the mineral on display Descriptions of some of the minerals, as they look in rocks, follow: Quartz: Quarts is the last mineral to crystallize, so in igneous rocks it never has any definite shape. In rocks, it does not show flat faces. It is usually gray in igneous rocks; gray, white, yellow, or red in sedimentary rocks; and gray or white in metamorphic rocks. It has a glassy look to it and comes in a great variety of colors and forms as seen on display. Feldspars: Feldspars are pink or tan, sometimes white. They show flat, shiny faces in igneous rocks (such as granite). The crystal grains are usually blocky and nearly rectangular. Feldspar might be the most abundant mineral in rock. It makes up as much as 50% of rocks. Micas: (muscovite, biotite, phlogopite) Micas have very thin layers that peel off (or cleave) very easily. In rocks they are usually flakes or layers of flakes. Muscovite is silvery to brown; biotite is black;
