1. Earth’s Buried Treasures
Earth Science
Earth’s Buried Treasures
An Introduction to Earth Materials: Minerals

2. The Importance of Minerals

3. Definition of a Mineral
A Mineral is:
Naturally Occurring
Inorganic
Solid
Definite chemical composition
Orderly internal arrangement of atom
Gemstones
Mineraloids lack an internal arrangement of atoms

4. Rocks vs. Minerals
Minerals are the components of rocks. A thorough understanding of minerals provide a better understanding of the formation of rocks.

5. Elements of the Earth’s Crust
An element is a substance that cannot be broken down into simpler, stable substances by chemical means. Each element has physical and chemical properties that can be used to identify it. The diagram above shows common elements in Earth’s crust. Approximately 90 elements occur naturally on Earth. Eight of these make up more than 98%of Earth’s crust.

6. Major Mineral Group: The Silicates
Oxygen and Silicon are the most abundant elements in the Earth’s crust so…
The Silicates are the most abundant group
Made up of the Silicon-Oxygen Tetrahedron
Identified by the SiO in the chemical formula
Example: AlSiO2

7. Other Mineral Groups
To determine the mineral group, look at the last part of the chemical formula

8. Other Mineral Groups

9. Mineral Resources
Earth’s crust contains useful mineral resources. The processes that formed many of these resources took millions of years. Many of these mineral resources are mined for human use. Mineral resources can be either metals, such as gold, Au, silver, Ag, and aluminum, Al, or nonmetals, such as sulfur, S, and quartz, SiO2.
If a volume of rock is enriched enough in an element or mineral to be potential valuable it is called a mineral deposit

10. Mineral Environments of Formation
Mineral Environments refers to the "geologic environments" in which minerals occur – the types of rocks in which they are found.  While some minerals occur in two or more environments, others tend to be restricted to a single environment. 
Example: If you think you have found the mineral kyanite in a sedimentary sandstone and see that it is a mineral formed by metamorphic processes you’ll know it can’t be kyanite.  Try celestite…  If you think you have found topaz in a cavity in basalt and read that it is largely restricted to pegmatite you’ll know it isn’t topaz.  And so on.
Chapter18.9

11. Mineral Environments of Formation
Ores form in a variety of ways, as shown below. Some ores, such as ores of chromium, Cr, nickel, Ni, and lead, Pb, form within cooling magma. As the magma cools, dense metallic minerals sink. As the minerals sink, layers of these minerals accumulate at the bottom of the magma chamber to form ore deposits.
By knowing how specific minerals and the environments in which they form you can make an interpretation of paleo-environments as well as locate mineral resources. You can also use this to differentiate between similar appearing minerals

12. Mineral Environments of Formation
The environments of mineral formation and growth are highly varied, ranging from slow crystallization at the high temperatures and pressures of igneous melts deep within the Earth's crust to the low temperature precipitation from a saline brine at the Earth's surface.
Various possible methods of mineral formation include:
- sublimation from volcanic gases
- deposition from aqueous solutions and hydrothermal brines
- crystallization from an igneous magma or lava
- recrystallization due to metamorphic processes and metasomatism
- crystallization during diagenesis of sediments
- formation by oxidation and weathering of rocks exposed to the atmosphere or within the soil environment.

13. Mineral Environments of Formation
18.09.c
Igneous crystallization
Hydrothermal deposition
EXPLANATION
Igneous crystallization can concentrate minerals by crystal settling
Hydrothermal deposition: from hot water along fracture (vein), hot springs, or vents on sea floor
Hydrothermal replacement: fluids permeate rock and replace original minerals with ore minerals
Metamorphism can allow new crystals to form, like these kyanite crystals used at one time for sparkplugs
Volcanism can bring up precious minerals formed at depth, like these diamond pipes
NOTES
Igneous crystallization: magnetite layer over anorthosite, Bushveld, South Africa
Hydrothermal deposition: gold vein, Oatman, Arizona
Hydrothermal replacement: Rooiberg tin mine, South Africa
Metamorphism: western Arizona
Volcanism: Kimberly, South Africa
Hydrothermal replacement
Volcanism and volcanic pipes
Metamorphism

14. Minerals Formed in Igneous Environments
Mineral Environments of Formation
Minerals Formed in Igneous Environments
Quartz Na/Ca Feldspar K Feldspar Mica
(Plagioclase) (Orthoclase) (Biotite)
Mica Amphibole Pyroxene Olivine
(Muscovite) 14

15. Minerals formed in Metamorphic Environments
Mineral Environments of Formation
Minerals formed in Metamorphic Environments
Quartz Na/Ca Feldspar K Feldspar Mica Mica
(Plagioclase) (Orthoclase) (Biotite) (Muscovite)
Serpentine Chlorite Garnet Calcite 15

16. Important Base Metal Deposits
Mineral Environments of Formation
Important Base Metal Deposits
Ores
Hematite (Iron) Galena (Lead) Bauxite (Aluminum)
Bornite (Copper) Sphalerite (Zinc) Apatite (Phosphorous Used in Fertilizers) 16

17. Where do Platinum deposits occur?
Mineral Environments of Formation
Where do Platinum deposits occur?
Most Platinum deposits are associated with mafic or ultramafic igneou rocks that come from the mantle and rose into the crust.
Pictured is the Bushveld Complex in South Africa. The dark layers are platinum and chromite and the light layers are anorthosite.

18. Two Other Types of Metal Deposits
Mineral Environments of Formation
Two Other Types of Metal Deposits
Mississippi Valley lead-zinc deposits
Sudbury nickel deposits
EXPLANATION
Mississippi Valley deposits have lead and zinc and formed by saline waters flowing through sedimentary rocks
Sudbury nickel deposits formed with layered intrusion, perhaps triggered by a meteorite impact that left behind joints called shatter cones
NOTES
Mississippi Valley photograph: fluorite, galena, and calcite from central U.S.
Shatter cones (from impact)
18.11.d

19. How do precious metal deposits form?
Mineral Environments of Formation
How do precious metal deposits form?
Veins from hot water
Veins in metamorphic rocks
Gold in gravel
EXPLANATION
Hydrothermal fluids deposit gold and silver in veins, commonly near volcanic centers or plutons
Veins can form during metamorphism and redistribute gold, or gold veins can be introduced later
Gold is dense and accumulates at bottom of river gravels
Some gold-bearing gravels have been buried, like in South Africa
Gold is so expensive that large volumes of rocks that are only a little bit rich in gold are mined
Gold is produced from large copper mines, adding more value to the copper ore
Gold-bearing conglomerates (placer deposits)
By-product gold
Low-grade gold deposits
18.10.a

20. Mineral Environments of Formation
Quartz Vein with Gold Deposits

21. Mineral Environments of Formation
Diamond Formation
Kimberlite is the type of rock typically associated diamonds
Diamonds do not originate from the metamorphism of coal but rather form in the mantle and are brought to the surface by geologic features called kimberlite pipes

22. Mineral Environments of Formation
Other sources of diamond formation:
Kimberlite Pipe (most common)
Subduction Zones
Asteroid Impact Sites
Meteorites (brought by meteorites)

23. Mineral Environments of Formation
Rubies are a form of corundum, a rare mineral made up of densely packed aluminum and oxygen atoms, which are normally colorless. When other atoms are substituted for a few of the aluminum ones, bright hues emerge. Small amounts of chromium impart the deep red color of ruby, traces of titanium and iron produce the stunning blue of sapphire, and chromium and ferric iron create the delicate orange shades of the extremely rare and costly padparadscha.

24. Mineral Environments of Formation Where do Copper Deposits form?
Porphyry copper deposits
Massive sulfide deposits
Sedimentary copper deposits
EXPLANATION
Porphyry copper deposits form near plutons below composite volcanoes
Massive sulfide deposits are formed by black smokers
Sedimentary copper deposits form in several ways, from groundwater
NOTES
Ore and porphyry: Boulder Mountains, Montana
Massive sulfide: Ansil deposit, Quebec, Canada
Copper: central Arizona
18.11.a

25. Mineral Environments of Formation
18.09.c
Formation by weathering
Weathering enrichment
EXPLANATION
Extreme weathering can leach away most material, concentrating less mobile elements such as nickel or aluminum (such as at this bauxite mine)
Elements can be leached from rocks by weathering, carried by groundwater, and deposited elsewhere (copper)
Transport in rivers or wave action on beaches can concentrate valuable minerals, such as diamond in these river gravels
Salt, gypsum, and other commodities can be precipitated in lakes and seas
NOTES
Formation by weathering: bauxite mine, eastern India
Weathering enrichment: Silverbell, Arizona
Mechanical concentration: Kimberly, South Africa
Low-Temp precipitation: Gypsum, Colorado
Mechanical concentration
Low-temperature precipitation

26. Minerals formed From Weathering
Mineral Environments of Formation
Important Minerals
Minerals formed From Weathering
Quartz Kaolinite
Hematite Bauxite 26

27. Mineral Environments of Formation
Gold that has been liberated by weathering and erosion get carried away by streams and deposit within placer deposits

28. Where do base metal deposits form?
Minerals as Indicators of Ancient Environments
Where do base metal deposits form?
Most of our iron ores are mined from formations called banded iron formations (BIF’s) . These iron and quartz rich layers are an indication of the Great Oxygenating event that occurred during the Precambrian 2 billion years ago
Other iron ore deposits form as magma intrudes into the crust and releases metal rich fluids

29. Evaporites and Precipitants
Mineral Environments of Formation
Evaporites and Precipitants
Gypsum and Halite are examples of evaporites. These minerals from in low temperature aqueous environments.
Calcite and Travertine are examples of precipitants. These minerals precipitate out of water under the correct environmental conditions.

30. Marine evaporite deposits in the United States
Minerals as Indicators of Ancient Environments
Gypsum and Halite are evaporites that form by the evaporation of ocean water. Thus these deposits indicate the location of ancient seas

31. Minerals as Indicators of Ancient Environments
This image, taken by the Mars Exploration Rover Opportunity's panoramic camera, is an approximate true-color rendering of the "Berry Bowl," a rock in the "Eagle Crater" outcrop that contains pebble-like hematite spherules
Marble-like hematite concretions litter the Navajo Sandstone surface in southern Utah's Grand Staircase-Escalante National Monument.

32. Minerals as Indicators of Ancient Environments

33. Earth’s Buried Treasures
Conclusion
Earth’s Buried Treasures
An Introduction to Earth Materials: Minerals