White.
Quartz is a color.
Yes, the sreak test is much more reliable identifier than color.
Quartz has a white streak.
A mineral that can scratch glass but not a streak plate is quartz. Quartz has a hardness of 7 on the Mohs scale, which allows it to scratch glass (which has a hardness of about 5.5) but is harder than the streak plate, typically made from porcelain, which has a hardness of around 6-7. Therefore, while quartz can leave scratches on glass, it will not produce a streak on a streak plate.
Amethyst is a violet form of quartz.
Rose quartz typically exhibits a pale to medium pink color with a white streak.
Quartz is colorless when pure, but can be found in all colors of the rainbow.
Impurities gives quartz its many beautiful colors.
White.
Pure quartz is colorless. Trace amounts of transition metal impurities in the quartz are what give it its color.
Yes, amethyst is a type of quartz that contains traces of iron impurities that give it its purple color.
White. All forms of quartz will have a white streak, regardless of specimen color.