Quartz and Amethyst minerals are both types of Silicon Dioxide. However, they have different chemical compositions and physical properties.
In its pure state, Quartz is colourless but when Iron replaces some silicon atoms, purple is formed in which purple Quartz is called Amethyst.
Quartz is found abundantly all over the world with various colours including white, yellow, grey, green, pink and purple whereas Amethyst is always purple from light lavender to a vibrant violet colour.
Brazilian Amethyst is generally a pale violet or mid-toned purple, whereas Uruguayan Amethyst have a highly saturated deep purple or with blue or red flashes. Richer colours will also be sold at a more premium price or are often used in finer jewellery.
It is believed that Amethyst is used for relieving stress, promotes calmness and tranquillity, while Clear Quartz possesses a high vibrational energy that is used during meditation, manifestation and amplifying other crystal properties when paired together.