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.
Gems Formed in the Earthâs Mantle. Knowledge of the earthâs mantle is still rather limited. However, the evidence shows that some gems actually form in the mantle. To do so, they need to crystallize at an extremely high temperature. The most notable examples of gems formed in the earthâs mantle are diamond and peridot. By studying the peridot deposits in Arizona, geologists now believe they were created on rocks floating in the mantle, approximately 20 to 55 miles below the surface. An explosive eruption brought them near the surface of the earth.