Human: How many different types of sand are there on Earth? Assistant: 
There are at least three main types of sand found on Earth. The first type is quartz sand, which is made up of grains of silica. Quartz sand is the most common type of sand and is found in a variety of colors including white, gray, brown, red, pink, and black. The second type of sand is feldspar sand, which is made up of grains of feldspar minerals. Feldspar sand has a more uniform color than quartz sand and can be found in shades of yellow, green, blue, purple, and pink. The third type of sand is mica-schist sand, which consists of grains of mica and schist. Mica-schist sand is usually light to dark green or gray in color.