Q1: What rock comes before quartzite in the rock cycle? What rocks or rock could come just after quartzite in the rock cycle?
Q2: A geologist finds a course grained rock with crystals arranged in rows. What can the geologist infer about how this formed and what group it belongs to?
http://en.wikipedia.org/wiki/Quartzite
both questions are answered in the first two paragraphs: streaks and rows are the same.
igneous,sedimentary,metamorphic
A1: In the rock cycle, quartzite is formed from the metamorphosis of quartz-rich sandstone. Therefore, the rock that comes before quartzite in the rock cycle is quartz-rich sandstone.
On the other hand, after quartzite in the rock cycle, various rocks can be formed depending on the geological processes involved. For example, if the quartzite undergoes further metamorphosis under high pressure and temperature, it can transform into a rock called gneiss. Gneiss is a foliated rock with bands or layers of different minerals. Alternatively, if the quartzite is subjected to melting and subsequent cooling, it can form an igneous rock called granodiorite. Granodiorite is composed of coarse-grained crystals of quartz, feldspar, and other minerals.
A2: If a geologist finds a coarse-grained rock with crystals arranged in rows, they can infer that this rock has undergone a special type of igneous rock formation called pegmatitic texture. Pegmatitic texture occurs when magma that is rich in water and volatile elements cools slowly, allowing for the growth of large crystals with well-defined boundaries.
Based on this inference, the geologist can conclude that the rock belongs to the pegmatite group. Pegmatites are igneous rocks characterized by their exceptional grain size, with crystals often exceeding one centimeter in diameter. They usually contain minerals such as quartz, feldspar, mica, and sometimes rare minerals like tourmaline, beryl, or spodumene.