Mineralogy Rock Flash Cards

Cinnabar
HgS
Earthy Reds and Films
Hardness of 2 to 2.5
Dull Luster
Scarlet Red Colors

Sphalerite
(Zn,Fe)S
Reddish brown to black
Hardness of 3.5 to 4
Shiny luster (like biotite or muscovite)
Distorted crystals and psuedo-octahedral twins

Galena
PbS
Lead Gray to Silver
Hardness of 2.5 to 2.8
Metallic Luster
Heavy and Cubic

Stibnite
Sb₂S₃
Steel Gray to Silver
Hardness of 2
Metallic Luster
Elongated Silver Splinters

Molybdenite
MoS₂
Opaque to Silver
Hardness of 1 to 1.5
Shiny Metallic Luster
Flexible Sheets, looks like flecks of galena in other rocks

Pyrite
FeS₂
Dark yellow to Bronzish Gold
Hardness of 6 to 6.5
Bright Metallic Luster
Looks like a mass of slightly darker gold

Pyrrhotite
Fe1₁-xS
Very Dark Yellow to Bronze, some oranges within
Hardness of 3.5 to 4.5
Dull Metallic Luster
Looks like a dark pyrite with no cubes

Chalcopyrite
CuFeS₂
Yellow Brass to Dark Metallic Gold, some reds within
Hardness of 3.5 to 4
Dull Metallic Luster
Commonly appears surrounded by other crystals (I.e. doline or quartz)

Marcasite
FeS₂
Pale Yellow and Lime Green
Hardness of 6 to 6.5
Slightly Metallic Luster
Forms Spearheads and Nodular faces ("Stalactite-like")

Sulfur
S
Lemon Yellow
Hardness of 1.5 to 2.5
Greasy Luster
Smells like rotten eggs

Gold
Au
Golden to Yellow Gold
Hardness of 2.5 to 3
Metallic Luster
Present mostly in small amounts / specks in other rocks

Copper
Cu
Copper Reddish (may have greens)
Hardness of 2.5 to 3
Dull Metallic Luster
Green Oxidation Colors

Graphite
C
Gray to Black
Hardness of 1 to 2
Dull Greasy Luster
Can write with a sample

Diamond
C
Opaque to Browns, Grays, and Blacks
Hardness of 10
Transparent Luster
Forms perfect octahedrons

Bornite
Cu₅FeS₄
Black to Dark Gray
Hardness of 3
Metallic Luster
Rainbow Luster in light

Orpiment / Realgar
AsS
Yellow (Orpiment), Orange (Realgar)
Hardness of 1.5 to 2
Rusty Luster
Orange-Yellow Mix

Arsenopyrite
FeAsS
Silvery to Whitish Gray
Hardness of 5.5 to 6
Metallic Luster
Looks like a silver/gray pyrite

Fluorite
CaF₂
Colorless to Yellowish Red to Bluish Black
Hardness of 4
Glassy Luster
Many colors, often forms perfect octahedrals

Sylvite
KCl
Colorless to Brownish Red to Bluish Black
Hardness of 2
Glassy / Epoxy luster
Hematite Inclusions cause it to most commonly be reddish brown

Halite
NaCl
Colorless to White-Yellow to Black
Hardness of 2.5
Opaque to Translucent Luster
Tastes like salt

Gibbsite (bauxite)
Al(OH)₃
Earthy Claylike Colors: White and Yellowish to reddish brown
Hardness of 1 to 3
Earthy Luster
Holds other sediments together, looks like conglomerate

Goethite
FeOOH
Brown to Black, some earthy reds and oranges within
Hardness of 5 to 5.5
Earthy to Metallic Luster
Has bubble like structures, can replace pyrite and form cubes

Limonite
Iron Hydroxide
Yellowish Brown to Earthy Browns, Reds, and Oranges
Hardness of 5 to 5.5
Earthy Luster
Rusty Mineral Coating

Brucite
Mg(OH)₂
Colorless to Yellowish White to Blue
Hardness of 2.5
Waxy Luster
Looks kind of like a yellowed talc, has a powdery look

Rutile
TiO₂
Yellow to Red to Brown to Black
Hardness of 6 to 6.5
Somewhat Metallic Luster
Appears as lines of crystals in rocks (often broken)

Spinel

MgAl₂O₄

_{Colorless to White/Pink to Light Blue to Black}

_{Hardness of 8}

_{Glassy Luster}

_{Forms perfect octahedrons}

Corundum

Al₂O₃

Wide Range from Transparent/Opaque to Blue, Yellow, Purple, Red, Green, Brown, Gray

Hardness of 9

Diamond Like Luster

Hexagonal, barrel shaped crystals

Pyrolusite

MnO₂

Black to Silver

Hardness of 6 to 6.5

Submetallic Luster

Fibrous, small crystals all over surface

Ilmenite

FeTiO₃

_{Black to Steel to Dark Brown}

_{Hardness of 5 to 6}

_{Submetallic Luster}

_{Flat and tabular}

Chromite

FeCr₂O₄

Black

Hardness of 5.5

Submetallic Luster

Forms black small octahedrals, often surrounded by olivine

Earthy Hematite

Fe₂O₃

_{Earthy Reds}

Hardness of 5.5 to 6.5

Earthy Luster

Grainy and Coarse

Specular Hematite

Fe₂O₃

_{Black to Steel to Dark Gray}

Hardness of 5.5 to 6.5

Metallic Luster

Forms stubby reflective rhombohedral crystals

Apatite

Ca-Phosphate

Colorless to yellow to green to brown to red to blue

Hardness of 5

Glassy to subresinous luster

Hexagonal prismatic crystals (elongated or stubby)

Gypsum

CaSO₄∙2H₂O

White - Gray to Yellowish to Brown to Clear

Softness of 2

Glassy to Silky Luster

Forms in sheets, elongated fibrous grains, and spearheads

Celestite

SrSO₄

Colorless to Milky White to Pale Blue to Yellowish

Hardness of 3 to 3.5

Glassy to Pearly Luster

Always a light to grey blue

Barite

BaSO₄

Colorless to Yellow to Red to Black to Green

Hardness of 2.5 to 3.5

Glassy Luster

Tabular and heavy like galena

Calcite

CaCO₃

Colorless to Semicolorless with variable colors within

Hardness of 3

Glassy to Pearly Luster

Rhombohedral crystals

Dolomite

CaMg(CO₃)₂

Colorless to Pink to White to Yellow

Hardness of 3.5 to 4

Glassy to Pearly Luster

Forms “saddle” faces

Aragonite

CaCO₃

White to Yellow to Reddish

Hardness of 3.5 to 4

Glassy Luster

Radiating prismatic crystals, twinned crystals look hexagonal, may replace skeletons

Rhodochrosite

MnCO₃

Hardness of 3.5 to 4.5

Glassy to Pearly Luster

Its really pink

Siderite

FeCO₃

Yellow to Dark Brown

Hardness of 3.5 to 4

Bright Glassy Luster

Goethite colored with curved striated faces

Azurite

Cu₃(CO₃)₂(OH)₂

Blue to Purple

Hardness of 3.5 to 4

Glassy to Diamond Luster

Purplish blue crystals / coating, often form with malachite

Malachite

Cu₂(CO₃)(OH)₂

Green

Hardness of 3.5 to 4

Glassy to Silky Luster

Green crystals / coating, appears with azurite

Nepheline

(Dont need to know formula)

White to Yellowish

Hardness of 5.5 to 6

Greasy Luster

White colored material, often with black specks or sodalite (blue stuff)

Sodalite

(Dont need to know formula)

Bright to Dark Blue

Hardness of 5.5 to 6

Glassy Luster

Deep blue colors with white veins, often present in nepheline

Albite

NaAlSi₃O₈

White - Opaque to Tan to Colorless

Hardness of 6 to 6.5

Glassy Luster

Lighter colors with exsolution lamellae AND striations

Anorthite

CaAl₂Si₂O₈

Dark Colors

Hardness of 6 to 6.5

Glassy Luster

Dark colors with striations

Sanadine

KAlSi₃O₈

Colorless to Whitish to Yellowish (sometime grayish)

Sandy Luster

Sand-like fine grain feel, often twinned

Orthoclase

KAlSi₃O₈

White to Pale Yellow to Tan

Earthy Luster

Common carlsbad twinning

Microcline

KAlSi₃O₈

White to Pink to Red to Yellowish to Blue-Green

Glassy Luster

Hardness of 6 to 6.5

All have exsolution lamellae

Chalcedony

SiO₂

Browns and Tans w/ some opaque parts

Waxy Luster and Feel

Concentric Banding

Kinda looks like dead coral

Jasper

SiO₂

Red w/ Some Browns and Blacks

Waxy Luster and Feel

Matte to grainy reds

Chert

SiO₂

Dark Matte Colors - Blacks to Browns to Greens to Grays

Dull Waxy Luster and Feel

Opal

SiO₂ •nH₂O

Yellows, Whites, and Tans

Clear banding (if petrified wood)

Rose Quartz

SiO₂

Pink Quartz

Amethyst Quartz

SiO₂

Purple Quartz

Smokey Quartz

SiO₂

Quartz with grays and blacks

Milky Quartz

SiO₂

Quartz you cant see through it

Rock Quartz

SiO₂

Normal quartz

Talc

Mg₃Si₄O₁₀(OH)₂

White to Greenish White to Gray to Pinkish

Hardness of 1

Pearly Luster

Soapy feel, super easy to scratch

Pyrophyllite

Al₂Si₄O₁₀(OH)₂

White to Pale Green to Green-Brown

Hardness of 1 to 2

Greasy Luster to Pearly Luster

Radiating splinters

Epidote

Dont need to know formula

Shades of Green

Hardness of 6 to 7

Glassy Luster

Elongated splinters or small green crystals

Beryl

Be-silicate

White to Yellowish White to Blue-Green

Hardness of 7.5 to 8

Glassy luster

Hexagonal shaped often with striations

Tourmaline

Boron-Silicate

Varities of colors from Jet Black to Brown to Pink to Blue

Hardness of 7

Glassy Luster

Heavily Striated, forms hexagonal shapes

Cordierite

Dont need to know formula

Gray or Blue

Hardness of 7 to 7.5

Glassy Luster

Looks like sodalite w/ parallel contact twins and striations

Lepidolite

Lithium-Mica

Pink to Purple to Lilac Lamellae

Hardness of 2.5 to 4

Pearly Luster

Pink to purple small crystals, can form sheets

Kaolinite

Al₂Si₂O₅(OH)₄

Yellowish Gray to Brown to Yellowish White

Hardness of 2 to 2.5

Pearly Luster

Forms smooth surfaces

Serpentine

Mg₃Si₂O₅(OH)₄

Yellowish to Green / Dark Green

Hardness of 2.5 to 4

Greasy to Pearly Luster

Nonfoliated, can be striated or have fibrous bands

Muscovite

K(Al)₂AlSi₃O₁₀(OH)₂

Transparent to White to Yellow to Brown

Hardness of 2 to 2.25

Sheet Luster

Flexible, semi clear to mostly clear sheets (can also form opaque)

Biotite

K(Fe,Mg)₃AlSi₃O₁₀(OH)₂

Black to Brown to Dark Green, lines of yellow

Hardness of 2.5 to 3

Glassy Sheet Luster

Thin, dark resinous sheets

Chlorite

Dont need to know formula

Yellow-Green to Black

Hardness of 6.5

Glassy Luster

Dull green with some black, some samples looks like sheets or have layers in rock

Phlogopite

Dont need to know formula

Light Brown to Yellowish

Hardness of 2.5 to 3

Glassy Luster

Six sided sheets

Wollastonite

CaSiO₃

White to Grayish

Pearly Luster

Hardness of 4.5 to 5

Fibrous to needle like

Spodumene

Lithium - Silicate

Yellowish White to Gray (can be pink or green)

Glassy Luster

Hardness of 6.5 to 7

Heavy vertical striations

Rhodonite

Dont Need to Know Formula

Deep Pink

Glassy Luster

Hardness of 5.5 to 6.5

Pink w/ black veins & marks from manganese oxides

Augite (cpx)

Ca(Fe,Mg)Si₂O₆

Black to Greenish Black to Dark Brown

Resinous Luster

Hardness of 5 to 6

Psuedo - cubic / octahedral, polysynthetic twins cause “sheet like” characteristics

Diopside (cpx)

CaMgSi₂O₆

Pale Green to Blue to Whitish to Yellowish to Brown

Glassy Luster

Hardness of 5 to 6

“Book like” layers

Enstatite (opx)

MgSiO₃

Yellowish Brown to Dull Green to Olive

Glassy to Pearly Luster

Hardness of 5.5

Fibrous to plate-like

Hornblende

(KNa)Ca₂(Fe,Mg,Al)₅Al(Al,Si₆)O₂₂(OH)₂

Dark Green to Black

Glassy Luster

Hardness of 5 to 6

Needle-like / fibrous in aggregates

Tremolite

Ca₂Mg₅Si₈O₂₂(OH)₂

Colorless to White to Pale Gray to Greenish

Glassy to Silky Luster

Hardness of 5 to 6

Fibrous masses

Actinolite

Ca₂(Fe,Mg)₅Si₈O₂₂(OH)₂

Dark to Light Green

Glassy Luster

Hardness of 5 to 6

Almost fibrous, elongated prismatic crystals that are always a shade of green

Glaucophane

Dont need to know formula

Pale Blue-Gray to Dark Blue to Black

Glassy Luster

Hardness of 6 to 6.5

One perfect vertical cleavage, shades of gray-blue

Andalusite

Al₂SiO₅

“Flesh” Red to Brown to Red to Dark Olive Green

Glassy Luster

Hardness of 7.5

Forms rods that are a mix of colors, small rods in aggregates look fibrous / splinter-like, has an x in cross-section

Kyanite

Al₂SiO₅

Blue, may be white-gray to green to yellow

Glassy to Pearly Luster

Hardness of 4 to 5 or 6 to 7

Elongated tabular crystals that are darkest in the middle

Sillimanite

Al₂SiO₅

Mix of Grays, Browns, and Pale Greens

Glassy Luster

6 - 7

Slender fibrous crystals, forms aggregates which may be hard to see

Staurolite

Dont need to know formula

Reddish Brown to Black

Glassy to Resinous Luster

Hardness of 7 to 7.5

Resinous dark rhombus

Olivine

(Fe,Mg)₂SiO₄

Olive Green to Yellowish

Glassy Luster

Hardness of 6.5 to 7

Fine grain green rocks, may form prismatic green crystal faces

Titanite

Dont need to know formula

White to Yellow Green, Dark Brown or Black

Resinous Luster

Hardness of 5 to 5.5

Wedge shaped (monoclinic), darkly colored and resinous

Zircon

ZrSiO₄

Colorless to Yellow, Red, Brown, Gray, or Green

Diamond-like Luster

Hardness of 7.5

Tiny elongated octahedrals (requires handlense to see)

Almandine

Fe₃Al₂Si₃O₁₂

Bright or Dark Red

Hardness of 6.5 to 7

Diamond-like Luster

Stereotypical Garnet, forms good dodecahedrons or trapezohedrons

Pyrope

Mg₃Al₂Si₃O₁₂

Deep Purples, Reds, and Pinks

Hardness of 6.5 to 7.5

Glassy Luster

Small and rounded, pink to wine red to purple

Spessartine

Mn₃Al₂Si₃O₁₂

Light pastel pink

Glassy Luster

Looks like pink Garnet

Andradite

Ca₃Fe₂Si₃O₁₂

Salmon to Orange to Brown

Hardness of 6.5 to 7.5

Diamond-like Luster

Forms dodecahedral crystals that are salmon to orange colored, can also form opaque brown

Grossular

Ca₃Al₂Si₃O₁₂

Greenish Yellow to Cinnamon Brown

Hardness of 6.5 to 7.5

Glassy Luster

Forms dodecahedrals and trapezohedrals, often small crystal faces or masses

Uvarovite

Ca₃Cr₂Si₃O₁₂

Emerald Green

6.5 to 7.5

Sub Diamond-like Luster

Forms very small emerald green crystals, looks kinda like malachite