Chapter 5 Outline/Study Guide

Minerals of Earth’s Crust

Mineral – a natural inorganic solid that has a characteristic chemical compositionand physical properties.

Characteristics of Minerals

In order to determine if a substance is a mineral a scientist will ask the following questions

  1. Is the substance inorganic?
  2. Inorganic - not made up of living things or the remains of living things
  3. Does the substance occur naturally?
  4. minerals form and exist in nature, they are not manufactured (man made)
  5. Is the substance in crystalline form?
  6. atoms need to be arranged in a regularly repeating crystalline structure
  7. Does the substance have a consistent chemical formula?
  8. The ratio of the substances does not vary
  9. Is the substance a solid?

Therefore, a substance is not a mineral if it does not meet the above information. (ex. granite is not a mineral)

Kinds of Minerals

The two main groups of minerals are silicate and nonsilicate. The chemical composition of a mineral helps determine what group it belongs in.

Silicate minerals–(96% of Earth’s crust) a mineral that contains a combination of silicon and oxygen and may also contain one or more metals. (Examples – quartz, feldspars, orthoclase, plagioclase, ferromagnesian)

Silicates are the most common group of minerals.

Nonsilicate minerals - (4% of Earth’s crust) minerals that do not contain compounds of silicon and oxygen

Please answer the following questions on your own

What do you use to measure the hardness of a mineral?

What hardness does each item represent?

What is reclamation?

Make sure you are able to determine if an item is a mineral or not based on the characteristics of minerals.

Identifying Minerals (7 characteristics)

Process if identifying minerals

  1. color – most easily observed, but it is not a good identifier since color may change.
  2. luster – the way that a mineral reflects right(metallic, non-metallic, dull, vitreous, glassy, pearly, waxy)
  3. streak – the color of a mineral in powder form (you use a streak plate to help determine this)
  4. hardness – ability of a mineral to resist scratching. (Moh’s hardness scale)
  5. fracture – tendency of a mineral to break and form uneven, irregular surfaces.
  6. cleavage – tendency of a mineral to split and form flat, smooth surfaces.
  7. specific gravity – the ratio of the weight of the mineral to the weight of an equal volume of water – how heavy the mineral feels. (similar to density)

density – ratio of a substances mass to its volume.

Moh’s Hardness Scale

1 – talc(softest)

2 – gypsum

3 – calcite
4 – fluorite

5 – apatite

6 – feldspar

7 – quartz (hardest common mineral)

8 – topaz

9 – corundum

10 – diamond (hardest)

Special Properties of Minerals

Radioactive- when unstable atomic nuclei decay over time into stable nuclei.

If a mineral is fluorescentit shines under UV light.

Magnetism – the presence of iron-ore in mineral. This can be tested with a magnet. So if iron is in the mineral it will be magnetic.

Double refraction – when a clear mineral displays two images placed on top, found in calcite.