Final answer:
Minerals crystallize in a specific order based on their stability at different temperatures. Feldspar, which forms straight crystal sides, crystallizes first at high temperatures. Following feldspar, quartz then fills the remaining spaces and crystallizes at lower temperatures.
Step-by-step explanation:
The order in which minerals crystallize from highest temperature to lowest temperature is determined by the mineral's stability at certain temperatures. In general,
Feldspar crystallizes at the highest temperatures among common minerals. It usually forms early in the cooling process of magma, which means it crystallizes at a higher temperature compared to other minerals. Owing to the slow cooling process underground, feldspars often have well-formed, straight crystal sides.
Quartz tends to crystallize at lower temperatures following feldspar. As a later-forming mineral, quartz often fills the remaining spaces and does not have the straight edges that earlier-formed feldspar crystals do. Instead, quartz tends to have a glassy appearance.