World of Dinosaurs/Mineralogy/Feldspars

Feldspar is made of oxygen, silica, and lots of little cations, like calcium, potassium, etc. Here is a 3D model of a feldspar. This is another example of a slightly different feldspar. Attributes Feldspar is opaque with a greasy luster. One chemical form is a dusty pink. The other form is a dirty white. It forms as a trapezoid prisms - like cubes, but with a little bit of a lean. You can find big chunks - the size of a golf ball or racketball - while hiking in the mountains. Usually we see feldspar as the opaque bits of granite, as the opaque grains in sand, or as the dull and orange-y bits in sandstone. Feldspar is hard to scratch, hard to dissolve, and will break if a hammer hits it. It has a mix of ionic and covalent bonds. Dissolving or breaking feldspar is easier than dissolving or breaking quartz, but harder than mica. Broken feldspar will keep making smaller and smaller trapezoid prisms This is because there are lines of weakness formed by ionic bonds. The weak planes break, leaving crisp sides to the little baby trapezoids. Feldspar chunks can get sloppy edges. Chemical weathering can attack the edges of feldspar chunks. It's easier to dissolve feldspar than quartz. Tiny sand grains made of feldspar mineral might look a little bit more rounded off than their quartz neighbors. Where to find Feldspar and how it's formed Feldspar forms naturally without help from life in igneous rocks. It can form in magma that cools slowly, deep within Earth's crust. Examples include granite and diorite. Feldspar crystals are the opaque sections that look like white chocolate or have a pink hue. Importance in sedimentary rocks Sandy beaches in California, Oregon, and Washington include lots of quartz grains, and often an equal number of feldspar chunks. Feldspar forms by: Weathering the original rock where the feldspar formed, possibly an igneous granite; Transporting and breaking the feldspar in a river; Further breaking the feldspar as they shift at a beach. Feldspar CAN get destroyed by enough weathering and erosion. Extremely "mature" sand will have no feldspar, because it's been weathering and eroding for so long. You can tell how "mature" a sand, or the grains in a sandstone, are by: The minerals present How rounded-off the grains of feldspar and quartz look. More angular chunks means fresher grains, less travel, etc. More rounded-off means longer time or space traveled. Sand can make SANDSTONE in the right conditions