Mineral Formation 6 th Grade
Dec 23, 2015
Mineral Formation
6th Grade
Popcorn Rock Activity
• When the rock dolomite is doused in white distilled vinegar, aragonite crystals slowly form
A similar process occurs in Yellowstone National Park and in the Carlsbad Caverns in New Mexico
Carlsbad Caverns, New Mexico
Stala…WHAT?!
StalagMITE = on the ground –mighty and tall
StalacTITE = hanging from the ceiling –hanging tight to the ceiling
These form similarly to the “popcorn rock”
• Acid rain or water from other sources reacts with the rock such as limestone or dolomite
• This reaction hardens into a mineral
• “Popcorn rocks” appear on cavern walls, such as at the Lehman Caves
Lehman Caves
Crystals that often form from water added to rock are usually calcite and aragonite
What are 3 ways that minerals form?
• 1) form by magma and lava cooling
• 2) form by hot water solutions – solutions: elements and compounds that are
mixed with water
• 3) form by solutions evaporating
What is this called?
Geode = a rounded, hollow rock that is often lined with mineral crystals
Geode: How is it formed?
Formed when….• 1) a cavity forms in a rock –(an open space,
similar to a shell) –usually happen with rocks that are made from lava (the empty space is the gas bubbles)
Geode –crystals form when water containing dissolved minerals seeps into a crack or hollow in a rock
Minerals from Solutions
• Solution: a mixture in which one substance is dissolved in another
1) Minerals formed from Evaporation
• Minerals form when solutions evaporate
• Ex. If you stir salt crystals into a beaker or water, the salt dissolves, forming a solution. Eventually the solution evaporates, leaving behind salt crystals
• Ex. mineral halite formed over millions of years when ancient seas slowly evaporated– This happens in the US along the Midwest, Southwest, and
along the Gulf Coast
Halite –we use it in every day life!
Halite = table salt
Minerals formed from evaporation --gypsum
Minerals that can be formed by evaporation --Calcite
2) Minerals from Hot Water Solutions
• Deep underground, magma heats water to a high temperature
• When the water solution begins to cool, the elements and compounds leave the solution and crystalize as minerals
• Often PURE metals are formed this way
Minerals from Hot Water Solutions
• Vein = a narrow channel or slab or a mineral that is different from the surrounding rock
Gold Vein
• Remember that PURE METALS tend to form from hot water solutions underground, forming veins
• Ex. Gold, Silver, Platinum
Platinum
• Luster: metallic• Fracture: hackly • Hardness: 4.5• Streak: silver-grey• Cleavage: none
Silver
• Luster: metallic• Fracture: hackly• Hardness: 2.5 – 3• Streak: silver-white• Cleavage: none
3) Minerals formed from magma and lava:
• Minerals form: – As hot magma cools inside the crust– As lava hardens on the surface *When liquids cool to a solid state, they form crystals.
Tourmaline: a mineral that forms as magma cools deep beneath the surface
What influences the size of crystals?
The size of crystals depend on:
• The rate at which magma cools • The amount of gas the magma contains• The chemical composition of the magma
Magma closer to the surface cools FASTER (smaller crystals)
Magma deep within the crust cools SLOWLY (bigger crystals)
The size of a mineral depends on whether its high or low in the crust
• Large crystals –deep within the crust
• Small crystals --near the surface
http://www.youtube.com/watch?v=0OLdSJmvcUs
• Take a look!