Minerals are always found in the form of crystals.

Directions: Read the following passage and answer the following question.

What are crystals? They are actually minerals that could grow in to a particular shape that they were supposed to be. The shape of a crystal is determined by various factors. We now know that our DNA determines the color of our eyes, how tall we shall get to be and what shape our bones would ultimately take. In the same way it is the chemistry of a mineral, i.e. the chemicals that a mineral is made of, that determines what shape its crystals would ultimately take. Thus it is possible to tell different minerals apart by analyzing the shape of their crystals.
 
Sometimes minerals form in limited spaces where there is very little room, so they don't acquire a proper crystalline shape. When there is just a big hunk of a mineral, we call it a massive mineral. When there is a definite shape with easily observable flat sides or layers, we call it a mineral crystal.

Most of the   crystals found on the earth were formed millions of years ago. Crystals form when rocks in liquid form inside the earth slowly cool and harden under typical conditions.   Crystals also form when liquids beneath the ground find their way into cracks and slowly deposit minerals in due course of time. It takes thousands of years for most mineral crystals to grow” into their usual shapes but a few   salts (like halite) can form so quickly that one can watch them grow at one’s own home!

Many people think that crystals as clear pretty stones that are used for jewelry. Amethyst is a commonly found quartz crystal. Crystals not have to be clear, however, those are the kinds you may usually see in jewelry stores.