Jasper
Jasper is chert which is colored red or yellowish brown by iron oxides.
Granite
Close view of a granite hand specimen. Feldspar predominates. Quartz appears dark in the photograph, but shows glistening edges and points. From Graniteville.
Granite is a granular (coarse-grained) rock which has a glassy luster and is too hard to be scratched appreciably by steel. It may be white to gray, tan, brown, or pink to red in color, but pinkish to red granite predominates in Missouri. Some black stone, referred to locally as “black granite,” is usually a variety of gabbro. Most Missouri granite is coarse-grained, so that the constituent mineral grains—quartz, feldspar, and (less frequently) mica—can be readily recognized by anyone familiar with those minerals. It makes up many of the mountains and hills in Iron, Madison, and St. Francois counties and adjacent regions. North of the Missouri River, or where the glacial deposits remain, granite boulders may occur in the sandy and clayey glacial drift.
The mineral quartz is recognized in granite by its glistening, oily luster, really more brilliant than the luster of glass, and by its curved to irregular broken surface. Furthermore, the brilliant luster of quartz is not dulled by exposure to weather.
The mineral feldspar, in granite, has a glassy luster on the tiny flat cleavage faces where the individual grains are broken. Where weathered, feldspar becomes dulled, and chalky to dusty or clayey. Fresh feldspar may be glassy, white, buff, pink, red, in intermediate shades in color. With the mica, it imparts most of the color to granite.
Mica is recognized by its softness and its ability to be split very easily into tiny flakes. Other minerals may be found in granite under the microscope, but they have little importance or significance.
