NSSS4.2

toc =4.2 How Minerals Form=

Vocabulary

 * Solution**: A mixture in which a substance dissolves in another substance.
 * Vein**: A narrow channel of a mineral that is very different from the surrounding rock.

Introduction

 * Have you ever been to Crater National Park in Arkansas?
 * If you haven't, it is a park where you can search for diamonds.
 * So far, visitors have found more than 20,000 diamonds.

Processes That Form Minerals

 * Minerals can be formed by,
 * Crystallization of melted material
 * Crystallization of dissolved mineral

Minerals From Magma

 * When hot magma cools inside of the crust or when lava cools on the surface of the crust, minerals form
 * When they cool, they form crystals
 * The size of these crystals depends on
 * The cooling rate of the magma.
 * The amount of gas which the magma contains
 * The chemical composition of the magma
 * When magma deep below the surface cools slowly, over thousands of years, large crystals form
 * Magma closer to the surface cools faster then magma deep below the surface
 * Because of this rapid cooling, the crystals have less time to form thus being smaller

Minerals From Hot Water Solutions

 * When minerals dissolved in water ( which has been heated by magma ) cool, the elements and compounds leave the solution and crystallize as minerals.
 * When pure metals crystallize underground, they form veins
 * Veins form when solutions of hot water and metals follow cracks underground and crystallize.
 * Solutions usually form where tectonic plates spread apart along the mid-ocean ridge
 * First, water from the ocean seeps through cracks in the crust
 * Then, the water comes in contact with magma which heats it to a very high temperature.
 * After that, the heated water dissolves minerals in the crust and billows out of vents
 * Finally, the solution hits the cold sea and the minerals crystallize, sinking to the ocean floor.[[image:Ronaldo_soccer1jpg.jpg]]

Minerals Formed by Evaporation

 * When solutions evaporate, minerals can form
 * Deposits of the mineral halite have been formed the same way over millions of years

Where Minerals Are Found

 * Common minerals are spread evenly around the crust
 * Rarer and more valuable minerals are spread unevenly around the crust
 * Many valuable minerals are found near volcanic activity and mountain building

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