According to the Perceived Service Quality model (Figure 1), the quality of a service, as perceived by the customer, is the result of a comparison between the expectations of the customer and his or her real-life experiences.
Resorption of garnet I may have occurred either as a result of the prograde univariant reaction Grt + Chl + Ms = St + Bt + Qtz + H2O, or during decompression, by the net transfer reaction Grt + Ms + H2O = St + Bt + Qtz, before staurolite had become unstable.
Obsidian consists of silicon dioxide (Silica) that forms rock. Obsidian is not crystalline and therefore not a mineral. Obsidian forms from volcanic lava that has cooled to quickly for crystals to form. Obsidian is termed a natural volcanic glass and iron and magnesium impurities produce a black or dark green Obsidian. The presence of microscopic bubble patterns cause Obsidian to colour sheen.