Now that we know some of the identifying properties of minerals, 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?

Native Elements

The native elements 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. Below are some common examples of native element minerals:

MINERAL	COLOR(S)	STREAK	LUSTER	BREAKAGE	HARDNESS
Gold (Au) Precious Metal	Brassy yellow	Deep yellow	Metallic	Uneven Fracture	2.5 – 3.0
Silver (Ag) Precious Metal Fig. 3.3.2. “bonsai branch_ silver, copper, crystal gem” by subarcticmike is licensed under CC BY 2.0	Metallic gray	Light Gray	Metallic	None	2.5 -3.0
Copper (Cu) Economic Mineral, Industrial Use in Technology and Ores Fig. 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	Metallic	Uneven Fracture	2.5 – 3.0
Diamond (C) Precious Mineral, Conflict Resource	Clear, blue, brown, gray	None	Adamantine	Fracture	10
Graphite (C) Economic Mineral, pencil “lead” Fig. 3.3.5. “Graphite” by James St. John is licensed under CC BY 2.0	Light to dark gray	Dark gray	Greasy	Fracture	1.0 – 2.0
Sulfur (S) Economic Mineral used in explosives	Bright yellow	Colorless	Dull to Vitreous	Uneven to Conchoidal Fracture	1.5 – 2.5

Silicates

Minerals of the silicate 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 different types of silicate minerals, but below are the most common varieties.

MINERAL	COLOR(S)	STREAK	LUSTER	BREAKAGE	HARDNESS
Quartz (SiO2) Use in glassmaking, significant ingredient in sand	Variable	White	Vitreous	Conchoidal Fracture	7.0
Potassium Feldspar (KAlSi3O8) Fig. 3.3.8. “Orthoclase” by Photographer: John Bosworth is licensed under CC BY 4.0	Orange-pink (orthoclase) or blue-green (microcline)	White	Vitreous to Dull	2 cleavage directions at 90°	6.0
Plagioclase (NaAlSi3O8 to CaAl2Si2O8) Fig. 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
Muscovite (Mica) KAl2(AlSi3O10)(F,OH)2 Flaky, pulls apart in sheets	Clear, white, gray, tan	White	Vitreous	Basal Cleavage	2.0 – 2.5 (but breaks very easily!)
Biotite (Mica) K(Mg,Fe)3(AlSi3O10)(F,OH)2 Flaky, pulls apart in sheets	Black, dark gray, black-brown	White	Vitreous	Basal Cleavage	2.5 – 3.0 (but breaks very easily!)
Kaolinite (Clay) Al2Si2O5(OH)4 Key ingredient in porcelain/china Fig. 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
Talc (Clay) Mg3Si4O10(OH)2 Use in cosmetics and paint Fig. 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
Almandine (Garnet) Fe2+3Al2Si3O12	Dark red to purplish-red	White	Vitreous	Conchoidal Fracture	7.0 -7.5
Hornblende (Amphibole) (Ca,Na)23(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2 Fig. 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
Enstatite (Pyroxene) MgSiO3 Fig. 3.3.16.	Gray, green, brown, yellow	Gray	Vitreous	2 Cleavage directions at 90° Uneven Fracture	5.0 – 6.0
Olivine (Mg,Fe)SiO4 AKA Peridot	Green, sometimes Yellow-green	None	Vitreous	Conchoidal Fracture	6.5 – 7.0

Carbonates

Minerals in the carbonate 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. Below are some of the carbonate minerals you will most commonly encounter:

MINERAL	COLOR(S)	STREAK	LUSTER	BREAKAGE	HARDNESS
Calcite CaCO3 Main ingredient in limestone, fizzes with dilute acid, double refraction, sometimes fluoresces	Variable, but commonly colorless or white	White	Vitreous	3 Cleavage Directions; non-90° Conchoidal Fracture	3.0
Dolomite CaMg(CO3)2 Material in fossilized shells Fig. 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	Vitreous	3 Cleavage Directions; non-90°; Rhombohedral Conchoidal Fracture	3.5 – 4.0
Malachite Cu2CO3(OH)2 Always green	Green	Green	Vitreous to Dull	Basal Cleavage Uneven Fracture	3.5 – 4.0
Azurite Cu3(CO3)2(OH)2 Always blue Fig. 3.3.21. “File:Azurite from China.jpg” by Eric Hunt is licensed under CC BY-SA 2.5	Blue	Light Blue	Vitreous to Dull	2 Directions Conchoidal Fracture	3.5 – 4.0

Sulfates

Sulfate 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:

MINERAL	COLOR(S)	STREAK	LUSTER	BREAKAGE	HARDNESS
Gypsum CaSO4·2H2O Use in construction materials	Colorless, white, tan or yellowish	White	Vitreous, silky or waxy	3 Cleavage Directions, but one direction is perfect Conchoidal Fracture	2.0
Anhydrite CaSO4 Stable, dehydrated version of gypsum Fig. 3.3.23. “Anhydrite.” by Holly Leighanne. is licensed under CC BY 2.0	Variable: white, gray, pale blue, colorless	White	Vitreous to greasy	3 Cleavage Directions, almost cubic Conchoidal Fracture	3.5

Oxides

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!

MINERAL	COLOR(S)	STREAK	LUSTER	BREAKAGE	HARDNESS
Magnetite Fe2+Fe3+2O4 Magnetic mineral Fig. 3.3.24. “File:Magnetite-118736.jpg” by Rob Lavinsky, iRocks.com licensed under CC BY-SA 3.0	Black, Dark Gray	Black	Metallic	Uneven Fracture	5.5 – 6.5
Hematite Fe2O3 Heme means “blood”.	Dark Gray to Red-Brown	Red-Brown to Bright Red	Metallic	Uneven Fracture	5.5 – 6.5
Corundum Al2O3 AKA “Ruby” (when red), “Sapphire” (when blue)	Reddish pink to blue for gemstones, also brown to gray	Colorless	Adamantine to Vitreous	Fracture only	9.0
Ice H2O Only a mineral at freezing temperatures. Fig. 3.3.27. “Ice-cubes.” by rawdonfox is licensed under CC BY 2.0	Colorless, White, Pale Blue	White	Vitreous	Conchoidal Fracture	1.5

Sulfides

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

MINERAL	COLOR(S)	STREAK	LUSTER	BREAKAGE	HARDNESS
Pyrite FeS2  AKA “Fool’s Gold”	Brassy Yellow	Dark Gray to Brownish-Black	Metallic	Uneven Fracture	6.0 – 6.5
Galena PbS Heavy/ High density. Fig. 3.3.29. “Galena (Missouri, USA)” by James St. John is licensed under CC BY 2.0	Silver Gray to Dark Gray	Dark Gray	Metallic	3 Cleavage Directions at 90°; Cubic Near-Conchoidal Fracture	2.5 – 3.0

Halides

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

MINERAL	COLOR(S)	STREAK	LUSTER	BREAKAGE	HARDNESS
Halite NaCl Rock Salt, salty taste	Colorless, white	White	Vitreous	3 directions of perfect cleavage at 90°; Cubic Conchoidal Fracture	2.0 – 2.5
Fluorite CaF2 Often Fluorescent Fig. 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	Vitreous	6 directions; Octahedral Conchoidal Fracture	4.0

For Practice Only (Does not affect Knowledge Check Score!)