3.3 A Visual Guide to Common Minerals

Charlene Estrada

Now that we know some of the identifying properties of , we will go over some of the most common minerals we encounter on the Earth. Many of these are the main ingredients of rocks, and others have been extraordinarily useful in our society. What makes these minerals unique?

Video 3.3.1. The following brief lecture will show you the most common diagnostic properties of minerals (11:29).

Native Elements

The are a group of minerals that are composed of only one element. Many of these play a vital role in the global economy and industry. Table 3.3.1 contains common examples of native element minerals.

 

Table 3.3.1 Common native elements.
MINERAL COLOR(S) STREAK LUSTER BREAKAGE HARDNESS

(Au)

Precious Metal

Gold nugget interactive model
Figure 3.3.1. Gold nugget. Click on this image to go to a 3D interactive model by scrampunk (CC BY)
Brassy yellow Deep yellow Uneven 2.5 – 3.0

(Ag)

Precious Metal

bonsai branch_ silver, copper, crystal gem

Figure 3.3.2. “bonsai branch_ silver, copper, crystal gem” by subarcticmike is licensed under CC BY 2.0

Metallic gray Light Gray None 2.5 -3.0

(Cu)

Economic Mineral, Industrial Use in Technology and Ores

Large native copper amygdule (Mesoproterozoic, 1.05-1.06 Ga; Ahmeek Mine, Ahmeek, Upper Peninsula of Michigan, USA) 1

Figure 3.3.3. “Large native copper amygdule (Mesoproterozoic, 1.05-1.06 Ga; Ahmeek Mine, Ahmeek, Upper Peninsula of Michigan, USA) 1” by James St. John is licensed under CC BY 2.0

Bronze red-brown Red-Brown Uneven 2.5 – 3.0

(C)

Precious Mineral, Conflict Resource

Diamond Interactive Model
Figure 3.3.4. Polished Diamond. Click on this image to go to a 3D interactive model by joae12 (CC BY)
Clear, blue, brown, gray None 10

(C)

Economic Mineral, pencil “lead”

Graphite

Figure 3.3.5. “Graphite” by James St. John is licensed under CC BY 2.0

Light to dark gray Dark gray 1.0 – 2.0

(S)

Economic Mineral used in explosives

Sulfur Interactive Model
Figure 3.3.6. Sulfur. Click on this image to go to a 3D interactive model by rocks and minerals (CC BY)
Bright yellow Colorless Dull to Uneven to 1.5 – 2.5

Silicates

Minerals of the group are composed of some combination of silicon (Si) and oxygen (O). Silicate minerals make up the majority of the planet, both on the surface and within the interior. There are many types of silicate minerals, but below are the most common varieties.

 

Table 3.3.2 Common minerals in the silicate group.
MINERAL COLOR(S) BREAKAGE
(SiO2)

Use in glassmaking, significant ingredient in sand

Quartz interactive model
Figure 3.3.7. Cluster of quartz crystals. Click on this image to go to a 3D interactive model by geolab. unilasalle (CC BY-NC-SA)
Variable White 7.0
Potassium (KAlSi3O8)

Orthoclase

Figure 3.3.8. “Orthoclase” by Photographer: John Bosworth is licensed under CC BY 4.0

Orange-pink () or blue-green () White Vitreous to Dull 2 cleavage directions at 90° 6.0
(NaAlSi3O8 to CaAl2Si2O8)

Moonstone (iridescent peristerite-oligoclase feldspar) (Chupa Pegmatite Field, Mesoproterozoic, 1.75 to 2.10 Ga; at or near Chupa Bay, Karelia, Russia) 2

Figure 3.3.9. “Moonstone (iridescent peristerite-oligoclase feldspar) (Chupa Pegmatite Field, Mesoproterozoic, 1.75 to 2.10 Ga; at or near Chupa Bay, Karelia, Russia) 2” by James St. John is licensed under CC BY 2.0

Commonly white, sometimes blue White Vitreous 2 cleavage directions, non-90° 6.0 – 6.5
() KAl2(AlSi3O10)(F,OH)2

Flaky, pulls apart in sheets

Muscovite Interactive Model
Figure 3.3.10. Muscovite. Click on this image to go to a 3D interactive model by rocksandminerals (CC BY)
Clear, white, gray, tan White Vitreous Basal Cleavage 2.0 – 2.5 (but breaks very easily!)
(Mica) K(Mg,Fe)3(AlSi3O10)(F,OH)2

Flaky, pulls apart in sheets

Biotite interactive model.
Figure 3.3.11. Biotite. Click on this image to go to a 3D interactive model by rocksandminerals (CC BY)
Black, dark gray, black-brown White Vitreous Basal Cleavage 2.5 – 3.0 (but breaks very easily!)
() Al2Si2O5(OH)4

Key ingredient in porcelain/china

Kaolinite (Cretaceous; Twiggs County, Georgia, USA)

Figure 3.3.12. “Kaolinite (Cretaceous; Twiggs County, Georgia, USA)” by James St. John is licensed under CC BY 2.0

Commonly white or tan White Dull/Earthy Basal Cleavage 2.0 – 2.5
() Mg3Si4O10(OH)2

Use in cosmetics and paint

Talc schist 2

Figure 3.3.13. “Talc schist 2” by James St. John is licensed under CC BY 2.0

White, gray, clear, light green, brown White Waxy to greasy Basal Cleavage 1.0
() Fe2+3Al2Si3O12

Almandine Garnet interactive model.
Figure 3.3.14. Almandine garnets. Click on this image to go to a 3D interactive model by Lapworth Museum of Geology (CC BY-NC)
Dark red to purplish-red White Vitreous Conchoidal Fracture 7.0 -7.5
() (Ca,Na)23(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2

File:Magnesio-hornblende (cropped).png

Figure 3.3.15. “File:Magnesio-hornblende (cropped).png” by Creator:Robert Lavinsky is licensed under CC BY-SA 3.0

Black to dark green Light gray to white Vitreous to Dull 2 Cleavage directions at 56° and 124°

Uneven Fracture

5.0 – 6.0
() MgSiO3

File:Enstatite-pas-146a.jpg

Figure 3.3.16. Pyroxene, var. Enstatite

 

Gray, green, brown, yellow Gray Vitreous 2 Cleavage directions at 90°

Uneven Fracture

5.0 – 6.0
(Mg,Fe)SiO4

AKA

Olivine Interactive Model
Figure 3.3.17. Olivine. Click on this image to go to a 3D interactive model by UQ School of Earth and Environmental Science (CC BY)
Green, sometimes Yellow-green None Vitreous Conchoidal Fracture 6.5 – 7.0

Carbonates

Minerals in the group all have the elements carbon (C) and oxygen (O) arranged into what is called the carbonate anion, which is a carbon bonded with three oxygens: CO3–. Carbonate minerals play a key role in storing the world’s carbon dioxide, a greenhouse gas, in solid form. They also make up the “hard parts” of some animals such as shells in marine life. Table 3.3.3 shows some of the carbonate minerals you will most commonly encounter:

 

Table 3.3.3 Common minerals of the carbonate group.
MINERAL COLOR(S) BREAKAGE
CaCO3

Main ingredient in limestone, fizzes with dilute acid, double refraction, sometimes fluoresces

Calcite Interactive Model
Figure 3.3.18. Calcite. Click on this image to go to a 3D interactive model by Dr. Parvinder Sethi (CC BY)
Variable, but commonly colorless or white White 3 Cleavage Directions; non-90°

3.0
CaMg(CO3)2

Material in fossilized shells

File:Dolomite Eugui MNHN Minéralogie.jpg

Figure 3.3.19.File:Dolomite Eugui MNHN Minéralogie.jpg” by Marie-Lan Taÿ Pamart is licensed under CC BY-SA 4.0

White, colorless, gray, brown White 3 Cleavage Directions; non-90°; Rhombohedral

3.5 – 4.0
Cu2CO3(OH)2

Always green

Malachite Interactive Model
Figure 3.3.20. Malachite. Click on this image to go to a 3D interactive model by Malopolska`s Virtual Museums CC0 Public Domain.
Green Green to Dull Cleavage

Uneven

3.5 – 4.0
Cu3(CO3)2(OH)2

Always blue

image

Figure 3.3.21.File:Azurite from China.jpg” by E. Hunt is licensed under CC BY-SA 2.5

Blue Light Blue to Dull 2 Directions

 3.5 – 4.0

Sulfates

minerals are made of the elements sulfur (S) and oxygen (O) that are arranged into a sulfate ion: SO4–. Some of the most common sulfate minerals form within hot, dry environments when bodies of water, such as lakes, evaporate. These minerals build our homes and cities. Here are some of their properties below:

 

Table 3.3.4 Sulfate minerals
MINERAL COLOR(S) BREAKAGE
CaSO4·2H2O

Use in construction materials

Rock Gypsum Interactive Model
Figure 3.3.22. Click on this image to go to a 3D interactive model by EDUROCK – EDUCATIONAL VIRTUAL ROCK COLLECTION (CC BY)
Colorless, white, tan or yellowish White , or 3 Cleavage Directions, but one direction is perfect

Conchoidal Fracture

2.0
CaSO4

Stable, dehydrated version of gypsum

Anhydrite.

Figure 3.3.23. “Anhydrite.” by Holly Leighanne. is licensed under CC BY 2.0

Variable: white, gray, pale blue, colorless White to 3 Cleavage Directions, almost cubic

3.5

Oxides

are a mineral group that are defined by a combination of a metal cation bonded with oxygen (O). A lot of these minerals tend to be metallic and have found use in industry as sources of metal ores. However, this group also includes hydroxide minerals, which are minerals that contain oxygen bonded with hydrogen. Some of these minerals are used in our everyday lives!

 

Table 3.3.5 Common oxide minerals.
MINERAL COLOR(S) BREAKAGE
Fe2+Fe3+2O4

Magnetic mineral

Magnetite-118736.jpg

Figure 3.3.24.File:Magnetite-118736.jpg” by Rob Lavinsky, iRocks.com licensed under CC BY-SA 3.0

Black, Dark Gray Black Uneven 5.5 – 6.5
Fe2O3

Heme means “blood”.

Hematite Interactive Model.
Figure 3.3.25. Hematite. Click on this image to go to a 3D interactive model by rockdoc CC BY.
Dark Gray to Red-Brown Red-Brown to Bright Red Uneven 5.5 – 6.5

Al2O3

AKA “Ruby” (when red), “Sapphire” (when blue)

This mineral is 6-sided an reddish-purple. It can also be blue.
Figure 3.3.26. Corundum, var. “Ruby”
Reddish pink to blue for gemstones, also brown to gray Colorless to Fracture only 9.0
Ice H2O

Only a mineral at freezing temperatures.

Ice-cubes.

Figure 3.3.27. “Ice-cubes.” by rawdonfox is licensed under CC BY 2.0

Colorless, White, Pale Blue White 1.5

Sulfides

Minerals within the group all contain a metallic cation that is bonded with sulfur (S) as an anion. Nearly all the world’s ore materials can be found within the sulfide group. Metallic sulfides form in association with volcanic activity.

Table 3.3.6 Common sulfide minerals.
MINERAL COLOR(S) BREAKAGE
FeS2 

AKA “Fool’s Gold”

Pyrite Interactive model
Figure 3.3.28. Pyrite. Click on this image to go to a 3D interactive model by Earth Sciences, University of Newcastle CC BY-NC.
Brassy Yellow Dark Gray to Brownish-Black Uneven 6.0 – 6.5
PbS

Heavy/ High density.

Galena (Missouri, USA)

Figure 3.3.29. “Galena (Missouri, USA)” by James St. John is licensed under CC BY 2.0

Silver Gray to Dark Gray Dark Gray 3 Cleavage Directions at 90°; Cubic

Near-

2.5 – 3.0

Halides

Minerals in the group are composed of a cation element bonded with a anion element. Some of these minerals are known as salts because, like several , they form when water evaporates in hot, arid environments. One of the most well-known halides is something that we use in our kitchen every day!

 

Table 3.3.7. Common halides.
MINERAL COLOR(S) BREAKAGE
NaCl

Rock Salt, salty taste

Rock Salt/Halite Interactive Model
Figure 3.3.30. Rock Salt/Halite. Click on this image to go to a 3D interactive model by Dexter Perkins (CC BY-NC)
Colorless, white White 3 directions of perfect cleavage at 90°; Cubic

2.0 – 2.5
CaF2

Often

Fluorite (Denton Mine, near Cave-in-Rock, Illinois, USA) 2

Figure 3.3.31. “Fluorite (Denton Mine, near Cave-in-Rock, Illinois, USA) 2” by James St. John is licensed under CC BY 2.0

Variable White 6 directions; Octahedral

4.0