GENERAL GEOLOGY (GEOL 1113)

THE VIRTUAL ROCK BAG

Each semester at the University of Arkansas, students in General Geology courses are required to learn to identify a number of common minerals and rocks by their physical properties. To assist in this process, Sigma Gamma Epsilon (the honorary Geology organization) has traditionally prepared and sold Rock Bags containing samples of each of the minerals and rocks to be identified.

Now, for the first time, examples of the mineral and rock specimens are being made available as digital images on the World-Wide Web. NOTE: These images are intended to serve as a SUPPLEMENT to your learning and not as a SUBSTITUTE to hands-on learning with actual mineral and rock specimens. It is not recommended that you attempt to learn everything you need to know (such as various physical properties) about minerals and rocks from these pages - you should purchase a rock bag and practice your skills with the specimens while using these images as a study guide. With this in mind, I hope you will find these pages beneficial and enjoy the experiment!

There are a large number of images here, so this page may take awhile to load - please be patient (printing this page is not recommended)!

MINERAL GALLERY
IGNEOUS ROCK GALLERY
SEDIMENTARY ROCK GALLERY
METAMORPHIC ROCK GALLERY

MINERAL GALLERY

NAME: GALENA

COMPOSITION: Lead Sulfide

HARDNESS: <3

LUSTER/COLOR: Metallic Luster/Silver

CLEAVAGE: 3 @ 90o

STREAK: Dark Gray

REMARKS: very high specific gravity

 

NAME: MALACHITE

COMPOSITION: Copper Carbonate Hydroxide

HARDNESS: <4

LUSTER/COLOR: Vitreous/Bright Green

CLEAVAGE: 1, rarely observed

STREAK: Pale Green

REMARKS: common banded appearance

 

NAME: CHALCOPYRITE

COMPOSITION: Copper-Iron Sulfide

HARDNESS: <4

LUSTER/COLOR: Metallic luster/brass yellow

CLEAVAGE: none

STREAK: Greenish Black

REMARKS: generally distinguishable from pyrite by "tarnished" appearance

 

NAME: PYRITE

COMPOSITION: Iron Sulfide

HARDNESS: 6 - 6.5

LUSTER/COLOR: Metallic/Very Pale Brass yellow

CLEAVAGE: none

STREAK: Greenish Black to Brownish Black

REMARKS: "Fool's Gold"

 

NAME: HEMATITE

COMPOSITION: Iron Oxide

HARDNESS: 5.5 - 6.5

LUSTER/COLOR: Non-Metallic luster/Red

CLEAVAGE: none

STREAK: Red

REMARKS: Hematite also occurs with metallic luster (see below).

 

NAME: GARNET

COMPOSITION: Variable Fe, Mg, Mn,Ca silicate family

HARDNESS: 6.5 - 7.5

LUSTER/COLOR: Resinous/Red, Brown, Yellow, Green

CLEAVAGE: none

STREAK: white

REMARKS: Pictured here is a massive specimen(left) and a single crystal (right)

 

NAME: HORNBLENDE

COMPOSITION: Calcium-Sodium Magnesium-Iron Aluminum Silicate Hydroxide

HARDNESS: 5 - 6

LUSTER/COLOR: Vitreous/Black to Greenish Black

CLEAVAGE: 2, 60o and 120o

STREAK: Greenish Black to Brownish Black

REMARKS: distinguished from Augite by its cleavage angles

 

NAME: LIMONITE

COMPOSITION: Hydrated Iron Oxide

HARDNESS: <3

LUSTER/COLOR: Earthy/Brownish Yellow

CLEAVAGE: none

STREAK: Brownish Yellow

REMARKS: if you think it's dirt, it's probably Limonite

 

NAME: OLIVINE

COMPOSITION: Iron-Magnesium Silicate

HARDNESS: 6.5 - 7

LUSTER/COLOR: Vitreous/Olive Green

CLEAVAGE: none

STREAK: none

REMARKS: this specimen is actually a rock called Dunite, composed mostly of olivine.

 

  NAME: BIOTITE

COMPOSITION: Potassium Iron-Magnesium Silicate Hydroxide

HARDNESS: 2.5 - 3

LUSTER/COLOR: Vitreous/Black

CLEAVAGE: 1

STREAK: none

REMARKS: Biotite is a type of mica, a family of sheet silicates.

 

NAME: MUSCOVITE

COMPOSITION: Potassium Aluminum Silicate Hydroxide

HARDNESS: 2 - 2.5

LUSTER/COLOR: Vitreous/Colorless to Yellow

CLEAVAGE: 1

STREAK: none

REMARKS: Muscovite is a type of mica, a family of sheet silicates.

 

NAME: POTASSIUM FELDSPAR

COMPOSITION: Potassium Aluminum Silicate

HARDNESS: 6

LUSTER/COLOR: Vitreous/White to Pale Yellow to Pink

CLEAVAGE: 2 @ 90o

STREAK: none

REMARKS: This is a crystal cluster of the feldspar, Microcline

 

NAME: "PLAGIOCLASE"

COMPOSITION: Calcium-Sodium Aluminum Silicate

HARDNESS: 6

LUSTER/COLOR: Vitreous/Gray to White

CLEAVAGE: 2 @ 90o

STREAK: none

REMARKS: "Plagioclase" refers to a group of felspars containg calcium & sodium.

 

NAME: MASSIVE QUARTZ

COMPOSITION: Silicon Dioxide

HARDNESS: 7

LUSTER/COLOR: Vitreous/White, Pink, Yellow, Green, Purple, Black

CLEAVAGE: none

STREAK: none

REMARKS: The Quartz here is pink and called "Rose Quartz"

 

NAME: QUARTZ CRYSTAL

COMPOSITION: Silicon Dioxide

HARDNESS: 7

LUSTER/COLOR: Vitreous/White, Pink, Yellow, Green, Purple, Black

CLEAVAGE: none

STREAK: none

REMARKS: Nice crystal, eh?

 

NAME: HALITE

COMPOSITION: Sodium Chloride

HARDNESS: 2.5

LUSTER/COLOR: Vitreous/Clear

CLEAVAGE: 3 @ 90o

STREAK: none

REMARKS: Halite is the only mineral eaten by humans.

 

NAME: GYPSUM

COMPOSITION: Hydrated Calcium Sulfate

HARDNESS: 2

LUSTER/COLOR: Vitreous/Clear

CLEAVAGE: 1

STREAK: none

REMARKS: Gypsum is the main component in plaster and wall board.

 

NAME: CALCITE

COMPOSITION: Calcium Carbonate

HARDNESS: 3

LUSTER/COLOR: Vitreous/White to Clear

CLEAVAGE: 3, not at 90o

STREAK: none

REMARKS: Calcite is a very common mineral and the main mineral in limestone.

 

NAME: FLUORITE

COMPOSITION: Calcium Fluoride

HARDNESS: 4

LUSTER/COLOR: Vitreous/Purple

CLEAVAGE: 4

STREAK: none

REMARKS: Fluorite is one of my favorite minerals!

 

NAME: KAOLINITE

COMPOSITION: Aluminum Silicate Hydroxide

HARDNESS: 2

LUSTER/COLOR: Earthy/White

CLEAVAGE: 1, not usually observed

STREAK: none

REMARKS: A very common clay mineral, it is also the active ingredient in Kaopectate!

 

NAME: DOLOMITE

COMPOSITION: Calcium-Magnesium Carbonate

HARDNESS: 3

LUSTER/COLOR: Vitreous/White toPale Pink

CLEAVAGE: 3, not at 90o

STREAK: none

REMARKS: Commonly associated with calcite in limestones

 

NAME: MAGNETITE

COMPOSITION: Iron Oxide

HARDNESS: 6

LUSTER/COLOR: Sub-Metallic/Very Dark Gray to Black

CLEAVAGE: none

STREAK: Black

REMARKS: It really is magnetic.

 

NAME: CHLORITE

COMPOSITION: Magnesium-Iron Aluminum Silicate Hydroxide

HARDNESS: 2 - 2.5

LUSTER/COLOR: Pearly/Green to Blackish Green

CLEAVAGE: 1

STREAK: none

REMARKS: The name chorite is derived from the Greek word for 'green'

 

NAME: SPHALERITE

COMPOSITION: Zinc Sulfide

HARDNESS: 3.5 - 4

LUSTER/COLOR: Resinous/Yellowish Brown to Black

CLEAVAGE: 6

STREAK: White to Yellowish Brown

REMARKS: Sphalerite is a common ore mineral of zinc.

 

NAME: TALC

COMPOSITION: Magneisum Silicate Hydroxide

HARDNESS: 1

LUSTER/COLOR: Satin/White

CLEAVAGE: 1, not usually observed

STREAK: none

REMARKS: Finely-ground Talc is the main ingedient in talcum powder.

 

NAME: GOETHITE

COMPOSITION: alpha Iron Oxide Hydroxide

HARDNESS: 5 - 5.5

LUSTER/COLOR: Dull/Dark Brown to Brownish Black

CLEAVAGE: none

STREAK: Yellowish Brown

REMARKS: Named for the German poet, Goethe

 

NAME: PYRRHOTITE

COMPOSITION: Iron Sulfide

HARDNESS: 4

LUSTER/COLOR: Metallic/Brownish Bronze

CLEAVAGE: none

STREAK: Black

REMARKS: A similar mineral called Troilite is common in meteorites.

 

NAME: HEMATITE (Metallic)

COMPOSITION: Iron Oxide

HARDNESS: 5.5 - 6.5

LUSTER/COLOR: Metallic/Silver

CLEAVAGE: 1

STREAK: Red

REMARKS: The metallic variety of Hematite if often called 'Specularite'

 

 

NAME: GRAPHITE

COMPOSITION: Carbon

HARDNESS: 1 - 2

LUSTER/COLOR: Sub-Metallic/Dark Gray to Black

CLEAVAGE: 1

STREAK: Dark Gray to Black

REMARKS: unlike diamonds, Graphite can be manufactured from coal!

 

NAME: AUGITE

COMPOSITION: Calcium-Magnesium Aluminum Silicate

HARDNESS: 5 - 6

LUSTER/COLOR: Vitreous/Black

CLEAVAGE: 2 @ almost 90o

STREAK: none

REMARKS: Augite is the most common member of the pyroxenes.

 

NAME: AZURITE

COMPOSITION: Copper Carbonate Hydroxide

HARDNESS: 3.5 - 4

LUSTER/COLOR: Vitreous/Azure Blue

CLEAVAGE: none

STREAK: none

REMARKS: Azurite is charcterized by its deep blue color.


IGNEOUS ROCK GALLERY

NAME: GRANITE

COMPOSITION: Biotite/Muscovite, Potassium Feldspar, Quartz

TEXTURE: Phaneritic

ORIGIN: Intrusive

 

NAME: DIORITE

COMPOSITION: Biotite, Sodium Feldspar, Hornblende

TEXTURE: Phaneritic

ORIGIN: Intrusive

 

NAME: GABBRO

COMPOSITION: Pyroxene, Calcium Feldspar, Olivine

TEXTURE: Phaneritic

ORIGIN: Intrusive

 

NAME: RHYOLITE

COMPOSITION: Biotite/Muscovite, Potassium Feldspar, Quartz

TEXTURE: Aphanitic

ORIGIN: Extrusive

 

NAME: BASALT PORPHYRY

COMPOSITION: Pyroxene, Calcium Feldspar, Olivine

TEXTURE: Porphyritic

ORIGIN: Extrusive

 

NAME: ANDESITE

COMPOSITION: Biotite, Hornblende, Sodium Feldspar

TEXTURE: Aphanitic

ORIGIN: Extrusive

 

NAME: BASALT

COMPOSITION: Pyroxene, Calcium Feldspar, Olivine

TEXTURE: Aphanitic

ORIGIN: Extrusive

 

NAME: SCORIA

COMPOSITION: Pyroxene, Caclium Feldspar, Olivine

TEXTURE: Aphanitic

ORIGIN: Extrusive

 

NAME: OBSIDIAN

COMPOSITION: Glass

TEXTURE: Glass

ORIGIN: Extrusive

 

NAME: PUMICE

COMPOSITION: Glass

TEXTURE: Glass

ORIGIN: Extrusive


SEDIMENTARY ROCK GALLERY

NAME: BAUXITE

TYPE: Chemical Sedimentary Rock

Bauxite is an ore of aluminum and the State Rock of Arkansas.

 

NAME: CONGLOMERATE

TYPE: Clastic Sedimentary Rock

 

NAME: QUARTZ SANDSTONE

TYPE: Clastic Sedimentary Rock

 

NAME: BRECCIA

TYPE: Clastic Sedimentary Rock

 

NAME: DOLOSTONE

TYPE: Chemical Sedimentary Rock

.

 

NAME: MICRITE

TYPE: Chemical Sedimentary Rock

 

NAME: OOLITIC LIMESTONE

TYPE: Chemical Sedimentary Rock

Click button to see a microscopic view of Oolitic Limestone

Click button if you want to see where Oolitic Limestone forms

 

NAME: FOSSILIFEROUS LIMESTONE

TYPE: Chemical Sedimentary Rock

Click button if you want to see where Fossiliferous Limestone forms

 

NAME: CHALK

TYPE: Chemical Sedimentary Rock

 

NAME: SHALE

TYPE: Clastic Sedimentary Rock


METAMORPHIC ROCK GALLERY

NAME: SLATE

TEXTURE: Foliated

ORIGIN: metamorphosed shale

 

NAME: GNEISS

TEXTURE: Foliated

ORIGIN: metamorphosed shale

 

NAME: SCHIST

TEXTURE: Foliated

ORIGIN: metamorphosed shale

 

NAME: MARBLE

TEXTURE: Non-Foliated

ORIGIN: metamorphosed limestone

 

NAME: PHYLLITE

TEXTURE: Foliated

ORIGIN: metamorphosed shale

 

NAME: QUARTZITE

TEXTURE: Non-Foliated

ORIGIN: metamorphosed sandstone

 

NAME: ANTHRACITE COAL

TEXTURE: Non-Foliated

ORIGIN: metamorphosed coal