Quartz - one of the most common minerals on the planet - also one of the most useful and readily identifiable. The presence of trace amounts of various elements give quartz it's color.
Quartz crystals, also known as "Rock Crystal" - as a colourless transparent stone is origin of the term "rhinestone." Small, tumbled quartz stones were found in the bed of the river Rhine and initially thought to be diamonds. When it became apparent that these stones did not have the hardness of diamond, but were a passable simulation, the term "rhinestone" came to be synonymous with "imitation diamond."
Rose Quartz is a pink variation of Quartz. Rose quartz is one of the most popular of the quartz stones. The colour is due to trace amounts of titanium, iron or manganese. It is frequently strung on pink cord or cable to emphasis it's colour, which you may want to do for the same reason, or as a nod to tradition.
Smoky Quartz is named after its smoky colour. The colour varies from brown to black and sometimes smoky grey. Sunglasses, in the form of flat panes of smoky quartz were used in China in the 12th century.