Home >> Science & Nature >> Rocks & Minerals

How to Identify an Opaque Rock

Rocks and minerals are formed through many complicated chemical processes, resulting in a wide variety of shapes, colors, textures and densities. In rock identification, there are different characteristics scientists describe to differentiate between types of rocks, including what elements the sample is composed of, and optical properties such as color, transparency, luster, reflection, streak and florescence. With a little practice, anyone can identify and catalog rock types, and optical properties such as transparency are the simplest to learn.

Things You'll Need

Bright light
Rock sample(s)
Notebook

Instructions

- 1
  Make sure your light source provides you with a bright light. Florescent lights are best for this purpose, but an incandescent light also works.
- 2
  Label the samples and create a table of observations in your notebook.
- 3
  Turn on the light and hold the rock sample in your line of vision between the light and your eyes. Note how much light passes through the sample; this is what defines the rock's transparency. A transparent mineral such as a diamond does not block the light at all. If the light is fuzzy or blurred, the rock is considered translucent.If no light passes through the rock at all, it is an opaque rock.
- 4
  Record the light observation in the notebook along with any other things you notice, such as color and weight.
- 5
  Record variations in your sample to help with identification. For example, some rocks can be more or less translucent than others of the same type, and some rocks may have parts that range from transparent to opaque.

Rocks & Minerals