Quartz is the second most abundant mineral in the Earth's continental crust. In Europe and the Middle East, quartz has been used for thousands of years in jewelry and carvings. Rock Quartz is colorless and transparent or translucent ands the colored gemstone varieties include Citrine, Rose Quartz, Amethyst, and Smoky Quartz.These are all macrocrystalline Quartz , which just means that individual crystals are visible without magnification and this is the type that is transparent.
Microcrystalline or Cryptocrystalline Quartz have crystals which are visible only under high magnification. These types are usually translucent or opaque, Chalcedony is an example of the cryptocrystalline form. Other opaque gemstone varieties of the microcrystalline type include agate, onyx, carnelian and jasper.
Pictured are clusters of Amethyst and Smoky Quartz.