The purple crystal shown in the picture above is commonly called amethyst. Select which of the following elements combine in an extended crystal structure to form amethyst.

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.