3.3 Formation of Minerals
Minerals are all around you. They are used to make your house, your computer, even the
buttonsonyourjeans. But, wheredomineralscomefrom? Therearemanytypesofminerals,
and they do not all form in the same way. Some minerals form when salt water on Earth’s
surface evaporates. Others form from water mixtures that are seeping through rocks far
below your feet. Still others form when mixtures of really hot molten rock cool.
Lesson Objectives
- Describe how melted rock produces minerals.
- Explain how minerals form from solutions.
Formation from Magma and Lava
You are on vacation at the beach. You take your flip-flops off to go swimming because it is
one of the hottest days of the summer. The sand is so hot it hurts your feet, so you have to
run to the water. Imagine if it were hot enough for the sand to melt. Some minerals start
out in liquids that are that hot.
ThereareplacesinsideEarthwhererockwillmelt. MeltedrockinsidetheEarthisalsocalled
molten rock, ormagma. Magma is a molten mixture of substances that can be hotter than
1,000oC. Magma moves up through Earth’s crust, but it does not always reach the surface.
When magma erupts onto Earth’s surface, it is known aslava.As lava flows from volcanoes
it starts to cool, asFigure3.19shows. Minerals form when magma and lava cool.
Figure 3.19: Lava is melted rock that erupts onto Earth’s surface. ( 28 )