We use our senses of sight, hearing, smell, touch, and taste to become aware of the world around us. For example, we recognize a flower by noting its color, its fragrance, and the texture, shape, and arrangement of its petals. These are some of its characteristic properties. A mineral also has distinguishing properties, among them color, luster, and hardness, which help us identify it. Some minerals have a single outstanding property, such as the magnetism of magnetite, that makes them easier to recognize. But to identify most minerals, we need to determine not just one, but several properties. [Illustration: Chalcedony showing botryoidal form.] Color Color is one of the properties we notice first. The color of some minerals is always the same, and it helps us to identify them. But it is not a dependable property to use in identifying all minerals, because some contain impurities that change or hide the real color. Luster The luster is the way the surface of a mineral reflects light. The luster of a mineral may be _nonmetallic_, _submetallic_, or _metallic_. Mineral metals such as gold, silver, galena, and pyrite have a _metallic_ luster. A few minerals have a luster that is almost, but not quite metallic—their luster is _submetallic_. A mineral with a nonmetallic luster may look _vitreous_ (glassy), _silky_, _resinous_ (like resin), _greasy_, _earthy_ (dull), _pearly_, or _adamantine_ (brilliant). Transmission of Light Some minerals allow light to pass through them; others do not. A mineral is _transparent_ if you can see both light and objects through it, as through clear glass. If you can see only light, but no objects, as through frosted glass, the mineral is _translucent_. When you hold an _opaque_ mineral up to the light, it looks dark. No light at all comes through it, even through the thin edges. [Illustration: Transparent mineral.] Hardness