There‌‌are‌‌three‌‌classifications‌‌of‌‌rocks:‌i‌gneous‌,‌m
‌ etamorphic‌,‌‌and‌s
‌ edimentary‌.‌‌Any‌‌type‌‌of‌‌
rock‌‌can‌‌be‌‌transformed‌‌into‌‌another‌‌kind.‌‌Igneous‌‌rocks‌‌are‌‌created‌‌from‌‌solidified‌‌magma‌‌
(rock‌‌that‌‌has‌‌been‌‌melted‌‌inside‌‌the‌‌earth),‌‌sedimentary‌‌rocks‌‌are‌‌created‌‌when‌‌smaller‌‌bits‌‌of‌‌
rock‌‌or‌‌sand‌‌are‌‌cemented‌‌together,‌‌and‌‌metamorphic‌‌rock‌‌are‌‌formed‌‌when‌‌other‌‌types‌‌of‌‌
rocks‌‌are‌‌subjected‌‌to‌‌heat‌‌and‌‌pressure.‌ ‌
Igneous‌R
‌ ocks‌ ‌
There‌‌are‌‌two‌‌main‌‌classifications‌‌of‌‌igneous‌‌rocks:‌i‌ntrusive‌‌‌and‌e
‌ xtrusive‌‌‌rocks.‌ ‌
Intrusive‌‌rocks‌‌‌harden‌‌slowly‌‌beneath‌‌the‌‌surface‌‌of‌‌the‌‌earth,‌‌and‌‌often‌‌form‌‌large‌‌mineral‌‌
crystals‌‌within‌‌the‌‌rock.‌‌Granite‌‌is‌‌a‌‌good‌‌example‌‌of‌‌an‌‌intrusive‌‌rock.‌Porphyritic‌‌intrusive‌‌
rocks‌‌‌have‌‌large‌‌crystals‌‌embedded‌‌in‌‌a‌‌matrix‌‌of‌‌smaller‌‌crystals.‌‌Pegmatite‌‌is‌‌the‌‌only‌‌
porphyritic‌‌rock‌‌on‌‌the‌‌Science‌‌Olympiad‌‌list.‌ ‌
Extrusive‌‌rocks‌‌‌harden‌‌quickly‌‌during‌‌a‌‌volcanic‌‌eruption‌‌and‌‌are‌‌usually‌‌smooth-grained.‌‌
Basalt‌‌is‌‌the‌‌most‌‌common‌‌form‌‌of‌‌extrusive‌‌rock.‌ ‌
Sedimentary‌‌Rocks‌ ‌
Sedimentary‌‌rocks‌‌occur‌‌when‌‌smaller‌‌bits‌‌of‌‌rock‌‌and‌‌sand‌‌are‌‌cemented‌‌together.‌‌
Sedimentary‌‌rocks‌‌are‌‌either‌c‌ lastic‌‌‌or‌o
‌ rganic‌.‌ ‌
Clastic‌‌rocks‌,‌‌like‌‌sandstone,‌‌form‌‌from‌‌other‌‌rocks‌‌and‌‌minerals.‌ ‌
Organic‌‌rocks‌,‌‌like‌‌limestone‌‌and‌‌coal,‌‌form‌‌from‌‌the‌‌bodies‌‌or‌‌shells‌‌of‌‌organisms.‌ ‌
Metamorphic‌‌Rocks‌ ‌
Metamorphic‌‌rocks‌‌are‌‌composed‌‌of‌‌other‌‌rocks‌‌that‌‌have‌‌been‌‌subjected‌‌to‌‌heat‌‌and‌‌
pressure.‌‌These‌‌rocks‌‌often‌‌bear‌‌little‌‌resemblance‌‌to‌‌their‌‌parent‌‌rocks.‌ ‌
Minerals‌ ‌
By‌‌definition,‌‌minerals‌‌must‌‌have‌‌definite‌‌chemical‌‌and‌‌crystal‌‌structures.‌‌There‌‌are‌‌a‌‌large‌‌
variety‌‌of‌‌minerals,‌‌many‌‌of‌‌which‌‌are‌‌very‌‌common.‌‌In‌‌order‌‌to‌‌understand‌‌minerals,‌‌it‌‌is‌‌
helpful‌‌to‌‌understand‌‌basic‌‌chemistry‌‌and‌‌the‌‌periodic‌‌table‌‌(this‌‌is‌‌not‌‌covered‌‌on‌‌this‌‌page,‌‌
but‌‌can‌‌be‌‌found‌‌in‌‌any‌‌chemistry‌‌book).‌‌Each‌‌mineral‌‌can‌‌be‌‌classified‌‌by‌‌ten‌‌different‌‌
characteristics:‌g
‌ roup‌,‌f‌ormula‌,‌c‌ olor‌,‌s‌ treak‌,‌l‌uster‌,‌c‌ rystal‌‌structure‌,‌c‌ leavage‌,‌f‌racture‌,‌‌
hardness‌,‌‌and‌s‌ pecific‌‌gravity‌.‌ ‌
Definitions‌ ‌
Group‌ ‌
Minerals‌‌are‌‌organized‌‌into‌‌groups‌‌based‌‌on‌‌their‌‌chemical‌‌makeup.‌‌Native‌‌elements‌‌are‌‌
composed‌‌of‌‌a‌‌single,‌‌pure‌‌element;‌‌Sulfides‌‌contain‌‌sulfur,‌‌arsenic,‌‌tellurium,‌‌or‌‌selenium;‌‌
Oxides‌‌and‌‌Hydroxides‌‌contain‌‌oxygen‌‌compounds;‌‌Halides‌‌contain‌‌sodium,‌‌chlorine,‌‌fluorine,‌‌
iodine,‌‌or‌‌bromine;‌‌Carbonates‌‌and‌‌Borates‌‌contain‌‌the‌‌carbonate‌‌or‌‌borate‌‌groups;‌‌Sulfates‌‌
contain‌‌the‌‌sulfate‌‌group;‌‌Phosphates,‌‌Arsenates,‌‌and‌‌Vanadates‌‌contain‌‌one‌‌of‌‌those‌‌
chemical‌‌groups;‌‌Silicates‌‌and‌‌Tectosilicates‌‌contain‌‌the‌‌element‌‌silicon.‌ ‌
Formula‌ ‌
Each‌‌mineral‌‌has‌‌a‌‌definite‌‌chemical‌‌composition.‌‌For‌‌example,‌‌copper‌‌difluorite‌‌is‌‌CuF‌2.‌ ‌‌
Understanding‌‌the‌‌naming‌‌of‌‌formulas‌‌may‌‌require‌‌reviewing‌‌a‌‌chemistry‌‌textbook.‌ ‌
Color‌ ‌
Color‌‌is‌n
‌ ot‌‌‌a‌‌reliable‌‌way‌‌to‌‌identify‌‌minerals.‌‌Some‌‌minerals‌‌can‌‌be‌‌any‌‌color‌‌under‌‌the‌‌sun.‌‌
While‌‌color‌‌can‌‌sometimes‌‌be‌‌useful,‌‌do‌‌not‌‌rely‌‌on‌‌it!‌ ‌
Streak‌ ‌
Streak‌‌is‌‌the‌‌color‌‌when‌‌a‌‌rock‌‌is‌‌rubbed‌‌across‌‌an‌‌unglazed‌‌piece‌‌of‌‌porcelain.‌‌Streak‌‌is‌‌much‌‌
more‌‌useful‌‌than‌‌color‌‌because‌‌a‌‌mineral‌‌always‌‌has‌‌the‌‌same‌‌streak.‌ ‌
Luster‌ ‌
A‌‌mineral’s‌‌luster‌‌is‌‌the‌‌way‌‌it‌‌reflects‌‌light.‌‌Descriptions‌‌of‌‌luster‌‌are‌‌very‌‌subjective‌‌but‌‌are‌‌
sometimes‌‌useful.‌‌Common‌‌types‌‌of‌‌luster‌‌are‌‌vitreous‌‌(glassy),‌‌adamantine‌‌(brilliant‌‌or‌‌
gem-like),‌‌resinous‌‌(resin-like),‌‌greasy,‌‌pearly,‌‌waxy,‌‌and‌‌silky.‌ ‌
Crystal‌‌Structure‌ ‌
Crystal‌‌structure‌‌is‌‌the‌‌basic‌‌shape‌‌of‌‌a‌‌mineral‌‌as‌‌it‌‌grows.‌‌A‌‌good‌‌mineral‌‌book,‌‌like‌‌the‌‌
Peterson‌‌Field‌‌Guide,‌‌will‌‌describe‌‌the‌‌different‌‌crystal‌‌structures.‌‌Here‌‌are‌‌some‌‌of‌‌them:‌ ‌
Isometric‌‌‌-‌‌Three‌‌axes‌‌of‌‌symmetry,‌‌all‌‌at‌‌right‌‌angles‌‌to‌‌one‌‌another,‌‌and‌‌all‌‌of‌‌equal‌‌lengths.‌‌
Sometimes‌‌called‌‌cubic.‌ ‌
Tetragonal‌‌‌-‌‌Three‌‌axes‌‌of‌‌symmetry,‌‌all‌‌at‌‌right‌‌angles‌‌to‌‌one‌‌another,‌‌two‌‌of‌‌the‌‌same‌‌length‌‌
and‌‌one‌‌shorter.‌ ‌
Hexagonal‌‌(Trigonal)‌‌‌-‌‌Four‌‌axes‌‌of‌‌symmetry;‌‌three‌‌are‌‌of‌‌equal‌‌length‌‌and‌‌lie‌‌in‌‌the‌‌same‌‌
plane‌‌at‌‌120‌‌degrees,‌‌the‌‌other‌‌can‌‌be‌‌any‌‌length‌‌and‌‌lies‌‌at‌‌right‌‌angles‌‌to‌‌the‌‌others.‌‌(Note:‌‌
Trigonal‌‌is‌‌sometimes‌‌considered‌‌to‌‌be‌‌separate‌‌from‌‌hexagonal.)‌ ‌
Orthorhombic‌‌‌-‌‌Three‌‌axes,‌‌all‌‌at‌‌right‌‌angles‌‌to‌‌one‌‌another,‌‌of‌‌three‌‌different‌‌lengths.‌ ‌
Monoclinic‌‌‌-‌‌Three‌‌unequal‌‌axes,‌‌two‌‌at‌‌right‌‌angles,‌‌and‌‌the‌‌other‌‌inclined.‌ ‌
Triclinic‌‌‌-‌‌Three‌‌unequal‌‌axes,‌‌none‌‌of‌‌which‌‌are‌‌at‌‌right‌‌angles‌‌to‌‌any‌‌others.‌
Cleavage‌ ‌
When‌‌a‌‌mineral‌‌has‌‌the‌‌tendency‌‌to‌‌break‌‌along‌‌smooth,‌‌flat‌‌surfaces,‌‌it‌‌has‌‌cleavage.‌‌If‌‌the‌‌
break‌‌is‌‌perfectly‌‌smooth‌‌and‌‌shiny,‌‌it‌‌is‌‌said‌‌to‌‌have‌‌perfect‌‌cleavage.‌‌Cleavage‌‌can‌‌also‌‌be‌‌
described‌‌as‌‌good,‌‌distinct,‌‌or‌‌poor.‌ ‌
Fracture‌ ‌
Fracture‌‌is‌‌described‌‌as‌‌the‌‌way‌‌a‌‌mineral‌‌breaks‌‌(not‌‌along‌‌a‌‌cleavage‌‌plane).‌‌It‌‌can‌‌be‌
uneven,‌‌hackly‌‌(sharp,‌‌jagged‌‌surface‌‌like‌‌broken‌‌metal),‌‌splintery,‌‌or‌‌conchoidal‌‌(shell-like).‌ ‌
Hardness‌ ‌
The‌‌Moh’s‌‌Hardness‌‌Scale,‌‌which‌‌is‌‌used‌‌by‌‌most‌‌mineral‌‌collectors,‌‌is‌‌based‌‌on‌‌the‌‌hardness‌‌
of‌‌other‌‌minerals.‌‌It‌‌is‌‌on‌‌a‌‌scale‌‌of‌‌one‌‌to‌‌ten,‌‌ten‌‌being‌‌the‌‌hardest.‌‌To‌‌test‌‌two‌‌minerals‌‌
against‌‌each‌‌other,‌‌try‌‌to‌‌scratch‌‌each‌‌mineral‌‌with‌‌the‌‌other‌‌in‌‌an‌‌inconspicuous‌‌place.‌‌If‌‌they‌‌
both‌‌scratch‌‌each‌‌other,‌‌they‌‌have‌‌the‌‌same‌‌hardness.‌‌If‌‌only‌‌one‌‌causes‌‌a‌‌scratch,‌‌it‌‌is‌‌the‌‌
hardest.‌‌Or,‌‌you‌‌can‌‌use‌‌common‌‌objects‌‌to‌‌see‌‌if‌‌the‌‌scratch‌‌or‌‌can‌‌be‌‌scratched‌‌by‌‌a‌‌mineral.‌ ‌
Specific‌‌Gravity‌ ‌
Specific‌‌gravity‌‌(SG)‌‌is‌‌a‌‌measure‌‌of‌‌how‌‌dense‌‌a‌‌mineral‌‌is.‌‌It‌‌compares‌‌the‌‌mass‌‌of‌‌one‌‌gram‌‌
of‌‌the‌‌mineral‌‌to‌‌the‌‌mass‌‌of‌‌one‌‌gram‌‌of‌‌water.‌‌So‌‌a‌‌mineral‌‌with‌‌a‌‌SG‌‌of‌‌4.5‌‌is‌‌4.5‌‌times‌‌as‌‌
heavy‌‌as‌‌water.‌‌With‌‌practice,‌‌you‌‌can‌‌tell‌‌whether‌‌a‌‌mineral‌‌specimen‌‌is‌‌"light"‌‌(usually‌‌less‌‌
than‌‌3.5)‌‌or‌‌"heavy"‌‌(greater‌‌than‌‌4).‌‌Specific‌‌gravity‌‌can‌‌be‌‌helpful‌‌in‌‌detecting‌‌metallic‌‌
minerals‌‌(which‌‌are‌‌usually‌‌heavier),‌‌or‌‌cases‌‌where‌‌a‌‌mineral‌‌is‌‌unusually‌‌heavy.‌‌For‌‌example,‌‌
galena‌‌is‌‌a‌‌gray,‌‌metallic‌‌mineral‌‌with‌‌a‌‌high‌‌lead‌‌content,‌‌and‌‌it‌‌is‌‌noticeably‌‌heavy.‌‌Specific‌‌
gravity‌‌is‌‌especially‌‌useful‌‌in‌‌the‌‌case‌‌of‌‌barite,‌‌a‌‌white‌‌mineral‌‌which‌‌is‌‌unusually‌‌heavy‌‌
because‌‌it‌‌contains‌‌the‌‌heavy‌‌metal‌‌barium,‌‌but‌‌does‌‌not‌‌look‌‌metallic‌‌at‌‌all.‌ ‌
This‌‌page‌‌does‌‌not‌‌list‌‌the‌‌characteristics‌‌of‌‌every‌‌mineral;‌‌however,‌‌more‌‌information‌‌can‌‌be‌‌
found‌‌in‌‌any‌‌good‌‌mineral‌‌identification‌‌handbook.‌‌Learning‌‌every‌‌characteristic‌‌of‌‌every‌‌
mineral‌‌is‌‌possible,‌‌but‌‌it‌‌is‌‌a‌‌good‌‌idea‌‌to‌‌only‌‌try‌‌and‌‌memorize‌‌the‌‌one‌‌distinguishing‌‌
characteristic‌‌of‌‌each‌‌mineral.‌‌Short‌‌descriptions‌‌that‌‌help‌‌remembering‌‌minerals‌‌are‌‌also‌‌a‌‌
good‌‌idea.‌ ‌
Mineral‌N
‌ ame‌‌Description‌ ‌
More‌‌Rocks‌‌and‌‌Minerals‌‌Descriptions‌ ‌
Albite‌‌‌-‌‌white,‌‌tan,‌‌or‌‌cream‌‌feldspar‌ ‌
Almandine‌‌‌-‌‌dark‌‌red,‌‌garnet‌ ‌
Amazonite‌‌‌-‌‌bright‌‌green‌‌feldspar‌ ‌
Apatite‌‌‌-‌‌usually‌‌green‌‌or‌‌purple,‌‌but‌‌can‌‌be‌‌almost‌‌any‌‌color‌ ‌
Aragonite‌‌‌-‌‌white,‌‌powdery‌‌variety‌‌of‌‌calcite.‌‌can‌‌often‌‌form‌‌amber‌‌colored‌‌hexagonal‌‌crystals‌ ‌
Augite‌‌‌-‌‌one‌‌of‌‌the‌‌approximately‌‌six‌‌minerals‌‌on‌‌the‌‌list‌‌that‌‌look‌‌like‌‌nondescript‌‌black‌‌rocks;‌‌
however,‌‌it‌‌has‌‌a‌‌greenish‌‌tinge‌‌and‌‌cleavage‌‌at‌‌a‌‌right‌‌angle‌‌that‌‌set‌‌it‌‌apart‌‌a‌‌little‌ ‌
Azurite‌‌‌-‌‌always‌‌blue‌‌(one‌‌of‌‌those‌‌minerals‌‌where‌‌color‌‌can‌‌be‌‌depended‌‌on),‌‌with‌‌a‌‌blue‌‌
streak‌ ‌
Bauxite‌‌‌-‌‌tan‌‌rock‌‌with‌‌orange,‌‌white,‌‌and‌‌prown‌‌pisoliths‌‌of‌‌aluminum,‌‌causing‌‌light‌‌weight,‌‌
formed‌‌from‌‌weathering‌‌of‌‌feldspars‌ ‌
Barite‌‌‌-‌‌white‌‌and‌‌kind‌‌of‌‌platy,‌‌but‌‌very‌‌heavy‌‌because‌‌it‌‌contains‌‌barium.‌‌can‌‌form‌‌rosettes‌ ‌
Beryl‌‌‌-‌‌the‌‌cheap‌‌specimens‌‌usually‌‌seen‌‌in‌‌Science‌‌Olympiad‌‌are‌‌mostly‌‌light‌‌green‌‌and‌‌
opaque;‌‌often‌‌have‌‌hexagonal‌‌crystal;‌‌aquamarine‌‌and‌‌emerald‌ ‌
Biotite‌‌‌-‌‌black‌‌mica‌‌–‌‌thin‌‌and‌‌platy;‌‌comes‌‌off‌‌in‌‌thin‌‌sheets‌ ‌
Bornite‌‌‌-‌‌"Peacock‌‌Copper;"‌‌has‌‌a‌‌dark,‌‌purplish-blue‌‌tarnish,‌‌also‌‌called‌‌Peackock‌‌Tarnish;‌‌
chalcopyrite,‌‌which‌‌looks‌‌almost‌‌the‌‌same,‌‌tarnishes‌‌purple,‌‌orange,‌‌yellow,‌‌and‌‌red‌ ‌
Calcite‌‌‌-‌‌looks‌‌almost‌‌like‌‌fluorite‌‌and‌‌can‌‌be‌‌any‌‌color,‌‌but‌‌it‌‌is‌‌a‌‌little‌‌softer‌‌and‌‌it‌‌has‌‌a‌‌more‌‌
rhombus‌‌like‌‌shape.‌‌It‌‌also‌‌bubbles‌‌in‌‌hydrochloric‌‌acid‌‌(hcl),‌‌but‌‌most‌‌people‌‌do‌‌not‌‌have‌‌that‌‌
lying‌‌around‌‌to‌‌test‌‌rocks‌‌with‌ ‌
Celestite‌‌‌-‌‌usually‌‌a‌‌soft,‌‌translucent‌‌white‌‌or‌‌blue‌ ‌
Chalcopyrite‌‌‌-‌‌very‌‌brassy‌‌yellow,‌‌tarnishes‌‌bright‌‌red,‌‌purple,‌‌yellow,‌‌and‌‌orange‌ ‌
Copper‌‌‌-copper‌‌color,‌‌see‌‌the‌‌green‌‌tarnish‌ ‌
Corundum‌‌‌-‌‌very‌‌hard‌‌reddish‌‌or‌‌purplish‌‌rock,‌‌very‌‌hard‌‌and‌‌often‌‌has‌‌small‌‌column-like‌‌
opaque‌‌crystals,‌‌rubies‌‌and‌‌sapphires‌ ‌
Diamond‌‌‌-‌‌adamantine‌‌luster,‌‌comes‌‌in‌‌various‌‌lighter‌‌colors,‌‌hardest‌‌mineral‌ ‌
Dolomite‌‌‌-‌‌thin,‌‌platy‌‌cream-colored‌‌crystals;‌‌sometimes‌‌there‌‌are‌‌dark‌‌specks‌‌embedded‌‌
between‌‌the‌‌crystals‌ ‌
Epidote‌‌‌-‌‌mostly‌‌greenish-yellow‌‌and‌‌grainy,‌‌but‌‌can‌‌be‌‌almost‌‌any‌‌shade‌‌of‌‌green;‌‌often‌‌
confused‌‌with‌‌olivine;‌‌described‌‌as‌‌"pistachio"‌ ‌
Feldspar‌‌‌-‌‌kind‌‌of‌‌a‌‌salmon-pink‌‌color;‌‌has‌‌a‌‌very‌‌distinctive‌‌luster‌ ‌
Flourite‌‌‌-‌‌almost‌‌any‌‌color;‌‌hard‌‌to‌‌distinguish‌‌from‌‌calcite,‌‌but‌‌it‌‌is‌‌a‌‌little‌‌harder;‌‌usually‌‌has‌‌
dipyramidal‌‌or‌‌cubic‌‌structure‌ ‌
Galena‌‌‌-‌‌has‌‌perfect‌‌cubic‌‌cleavage‌‌and‌‌is‌‌very‌‌heavy,‌‌made‌‌of‌‌lead‌‌sulfide‌‌and‌‌is‌‌an‌‌important‌‌
lead‌‌ore‌ ‌
Goethite‌‌‌-‌‌another‌‌"black‌‌rock",‌‌sometimes‌‌has‌‌a‌‌slightly‌‌iridescent‌‌tarnish,‌‌though,‌‌has‌‌been‌‌
described‌‌as‌‌an‌‌"ugly‌‌brownish‌‌orange-black‌‌rock"‌ ‌
Gold‌‌‌-‌‌gold‌‌colored,‌‌do‌‌not‌‌confuse‌‌with‌‌pyrite,‌‌typically‌‌smoother‌‌than‌‌pyrite,‌‌generally‌‌forms‌‌
nuggets‌‌while‌‌pyrite‌‌usually‌‌forms‌‌cubic‌‌crystals‌ ‌
Graphite‌‌‌-‌‌silver,‌‌shiny,‌‌soft,‌‌and‌‌leaves‌‌dark‌‌smudges‌‌on‌‌your‌‌hands,‌‌used‌‌for‌‌pencil‌‌lead.‌ ‌
Gypsum‌‌‌-‌‌looks‌‌like‌‌any‌‌number‌‌of‌‌transparent‌‌colorless‌‌minerals,‌‌but‌‌luckily‌‌gypsum‌‌is‌‌very‌‌
soft‌‌and‌‌easily‌‌scratched‌‌with‌‌your‌‌fingernail;‌‌alabaster‌‌gypsum‌‌is‌‌white‌‌and‌‌opaque,‌‌satin-spar‌‌
is‌‌white‌‌and‌‌fibrous,‌‌and‌‌selenite‌‌is‌‌transparent‌ ‌
Halite‌‌‌-‌‌rock‌‌salt;‌‌about‌‌the‌‌color‌‌and‌‌hardness‌‌of‌‌selenite‌‌gypsum;‌‌it‌‌has‌‌nice‌‌cubic‌‌crystals,‌‌
though,‌‌and‌‌you‌‌can‌‌usually‌‌identify‌‌it‌‌from‌‌that;‌‌tasting‌‌specimens‌‌is‌‌against‌‌the‌‌rules‌‌in‌‌
science‌‌olympiad,‌‌but‌‌smelling‌‌them‌‌is‌‌not‌‌and‌‌salt‌‌has‌‌a‌‌distinct‌‌smell‌‌along‌‌with‌‌a‌‌greasy‌‌feel‌ ‌
Hematite‌‌‌-‌‌hematite‌‌will‌‌either‌‌be‌‌black‌‌and‌‌shiny,‌‌dark‌‌gray‌‌and‌‌dull,‌‌or‌‌rusty‌‌red.‌‌Its‌‌most‌‌
distinctive‌‌feature‌‌is‌‌it‌‌is‌‌cherry‌‌red‌‌streak,‌‌but‌‌it‌‌also‌‌has‌‌one‌‌other‌‌interesting‌‌property.‌‌It‌‌is‌‌
almost‌‌always‌‌cool‌‌to‌‌the‌‌touch,‌‌much‌‌more‌‌than‌‌magnetite‌‌(which‌‌it‌‌looks‌‌like).‌ ‌
Hornblende‌‌‌-‌‌black‌‌with‌‌short‌‌stubby‌‌crystals,‌‌and‌‌usually‌‌striated‌‌lengthwise‌ ‌
Kaolinite‌‌‌-‌‌looks‌‌like‌‌chalk,‌‌but‌‌is‌‌actually‌‌clay;‌‌usually‌‌white‌‌and‌‌orange‌ ‌
Lepidolite‌‌‌-‌‌pink‌‌or‌‌lilac‌‌color;‌‌also‌‌has‌‌darker‌‌purple‌‌dots,‌‌called‌‌lamellae;‌‌a‌‌type‌‌of‌‌mica‌‌so‌‌it‌‌
is‌‌sometimes‌‌found‌‌in‌‌sheets‌ ‌
Magnetite‌‌‌-‌‌looks‌‌a‌‌lot‌‌like‌‌hematite,‌‌except‌‌it‌‌is‌‌magnetic;‌‌if‌‌you‌‌do‌‌not‌‌have‌‌the‌‌equipment‌‌to‌
check‌‌for‌‌that,‌‌it‌‌has‌‌a‌‌gray‌‌or‌‌black‌‌streak‌‌-‌‌hematite’s‌‌streak‌‌is‌‌cherry-red‌ ‌
Malachite‌‌‌-‌‌this‌‌mineral‌‌is‌‌easy‌‌because‌‌it‌‌is‌‌always‌‌green,‌‌with‌‌a‌‌green‌‌streak;‌‌often‌‌found‌‌
with‌‌azurite‌ ‌
Muscovite‌‌‌-‌‌white,‌‌yellow,‌‌or‌‌tan‌‌mica-thin‌‌and‌‌platy‌ ‌
Olivine‌‌‌-‌‌usually‌‌light‌‌green‌‌or‌‌yellowish-green,‌‌transparent‌‌specimens‌‌are‌‌called‌‌peridot‌ ‌
Opal‌‌‌-‌‌precious‌‌opal‌‌is‌‌iridescent,‌‌but‌‌most‌‌opal‌‌is‌‌white‌‌and‌‌opaque‌‌with‌‌a‌‌greasy‌‌or‌‌waxy‌‌
luster;‌‌usually‌‌amorphous‌‌crystals‌ ‌
Pyrite‌‌‌-‌‌metallic‌‌fool’s‌‌gold,‌‌often‌‌found‌‌in‌‌cubic‌‌or‌‌hexagonal‌‌crystals.‌‌It‌‌has‌‌a‌‌blackish‌‌green‌‌
streak.‌‌Distinguished‌‌from‌‌gold‌‌by‌‌greater‌‌hardness,‌‌lower‌‌specific‌‌gravity,‌‌rougher‌‌surface,‌‌and‌‌
tendency‌‌to‌‌form‌‌cubic‌‌crystals‌‌as‌‌opposed‌‌to‌‌nuggets‌ ‌
Quartz‌‌‌-‌‌fairly‌‌hard,‌‌no‌‌cleavage;‌‌agate‌‌is‌‌often‌‌grey‌‌or‌‌brown‌‌and‌‌is‌‌banded,‌‌onyx‌‌is‌‌a‌‌black‌‌
variety‌‌of‌‌agate,‌‌amethyst‌‌is‌‌purple‌‌and‌‌transparent,‌‌chalcedony‌‌is‌‌waxy,‌‌transparent‌‌grey‌‌and‌‌
usually‌‌found‌‌in‌‌bulbous‌‌masses,‌‌chert/flint‌‌is‌‌white/black‌‌and‌‌noncrystalline‌‌with‌‌a‌‌marked‌‌
conchoidal‌‌fracture,‌‌citrine‌‌is‌‌yellow‌‌or‌‌orange‌‌and‌‌transparent,‌‌crystal‌‌is‌‌colorless‌‌and‌‌
transparent,‌‌jasper‌‌is‌‌orange‌‌or‌‌red‌‌and‌‌opaque,‌‌milky‌‌is‌‌crystalline‌‌but‌‌white‌‌or‌‌light‌‌tan,‌‌rose‌‌is‌‌
pale‌‌pink‌ ‌
Rhodonite‌‌‌-‌‌comes‌‌in‌‌all‌‌shades‌‌of‌‌pink‌‌and‌‌red;‌‌usually‌‌massive,‌‌but‌‌sometimes‌‌crystalline‌ ‌
Silver‌‌‌-‌‌metallic‌‌silver‌‌color;‌‌pure‌‌form‌‌has‌‌the‌‌highest‌‌reflectiveness‌‌of‌‌any‌‌element,‌‌but‌‌it‌‌is‌‌
usually‌‌tarnished;‌‌this‌‌tarnish‌‌is‌‌silver‌‌sulfide‌‌and‌‌appears‌‌dull,‌‌dark‌‌gray‌ ‌
Sodalite‌‌‌-‌‌always‌‌blue,‌‌but‌‌usually‌‌a‌‌very‌‌dark,‌‌mottled‌‌blue;‌‌its‌‌darker‌‌color‌‌and‌‌colorless‌‌
streak‌‌tell‌‌it‌‌apart‌‌from‌‌azurite‌ ‌
Sphalerite‌‌‌-‌‌can‌‌be‌‌almost‌‌any‌‌color,‌‌but‌‌usually‌‌yellowish,‌‌tan,‌‌or‌‌reddish.‌‌It‌‌sometimes‌‌comes‌‌
in‌‌crystals,‌‌but‌‌it‌‌can‌‌be‌‌massive,‌‌too‌‌when‌‌it‌‌is‌‌usually‌‌a‌‌dark‌‌brown;‌‌has‌‌a‌‌resinous‌‌luster‌ ‌
Staurolite‌‌‌-‌‌almost‌‌always‌‌forms‌‌short,‌‌prismatic‌‌crystals;‌‌usually‌‌brown,‌‌and‌‌sometimes‌‌forms‌‌
cruciform‌‌twins‌ ‌
Sulfur‌‌‌-‌‌always‌‌some‌‌shade‌‌of‌‌yellow‌‌and‌‌it‌‌gives‌‌off‌‌a‌‌sulfurous‌‌odor‌‌when‌‌rubbed‌ ‌
Talc‌‌‌-‌‌very‌‌soft,‌‌often‌‌light‌‌green,‌‌white,‌‌or‌‌grey‌‌and‌‌feels‌‌very‌‌waxy‌ ‌
Topaz‌‌‌-‌‌extremely‌‌variable‌‌color‌‌but‌‌usually‌‌comes‌‌in‌‌well-formed‌‌prismatic‌‌crystals,‌‌a‌‌light‌‌
colored‌‌gem‌ ‌
Tourmaline‌‌‌-‌‌also‌‌extremely‌‌variable‌‌when‌‌it‌‌comes‌‌to‌‌color,‌‌but‌‌it‌‌often‌‌comes‌‌in‌‌long‌‌
prismatic‌‌crystals‌‌with‌‌vertical‌‌striations‌‌on‌‌it‌‌is‌‌surface;‌‌pleochroric‌‌(same‌‌crystal‌‌appears‌‌
different‌‌color‌‌depending‌‌on‌‌viewing‌‌angle)‌ ‌
Tremolite‌‌‌-‌‌usually‌‌comes‌‌in‌‌small,‌‌bladed‌‌crystals,‌‌light-colored‌‌and‌‌sometimes‌‌transparent,‌‌
commercially‌‌was‌‌used‌‌as‌‌asbestos‌ ‌
Ulexite‌‌‌-‌‌almost‌‌always‌‌white,‌‌and‌‌looks‌‌like‌‌a‌‌densely-packed‌‌bundle‌‌of‌‌white‌‌threads;‌‌opaque‌‌
in‌‌one‌‌direction‌‌and‌‌conducts‌‌light‌‌in‌‌the‌‌other;‌‌fiber-optic‌‌abilities‌‌gave‌‌it‌‌the‌‌nickname‌‌"T.V.‌‌
rock"‌ ‌
Bowen’s‌‌Reaction‌‌Series‌ ‌
Bowen’s‌‌Reaction‌‌Series‌‌‌is‌‌the‌‌work‌‌of‌‌Norman‌‌Bowen,‌‌a‌‌petrologist‌‌who‌‌conducted‌‌
experiments‌‌with‌‌heating‌‌rock‌‌material‌‌at‌‌different‌‌temperatures‌‌and‌‌analyzing‌‌results.‌‌The‌‌
reaction‌‌series‌‌helps‌‌explain‌‌why‌‌certain‌‌minerals‌‌are‌‌commonly‌‌found‌‌together,‌‌while‌‌others‌‌
combinations‌‌are‌‌rare‌ ‌
The‌‌series‌‌is‌‌broken‌‌in‌‌two‌‌branches,‌c
‌ ontinuous‌‌‌and‌d
‌ iscontinuous‌‌‌For‌‌the‌c‌ ontinuous‌‌
branch‌,‌‌the‌‌series‌‌explains‌‌that‌‌at‌‌the‌‌highest‌‌temperatures,‌‌calcium-rich‌‌Plagioclase‌‌will‌‌form.‌‌
As‌‌temperatures‌‌become‌‌cooler,‌‌sodium-rich‌‌Plagioclase‌‌will‌‌form,‌‌and‌‌Orthoclase,‌‌Muscovite,‌‌
and‌‌Quartz‌‌will‌‌follow‌‌For‌‌the‌d
‌ iscontinuous‌‌‌branch,‌‌the‌‌series‌‌says‌‌that‌‌Olivine‌‌will‌‌form‌‌at‌‌the‌‌
highest‌‌temperatures,‌‌followed‌‌by‌‌Pyroxene,‌‌Amphibole,‌‌and‌‌Biotite.‌‌After‌‌Biotite,‌‌the‌‌branch‌‌
produces‌‌Orthoclase,‌‌Muscovite,‌‌and‌‌Quartz,‌‌like‌‌the‌‌continuous‌‌branch‌‌describes‌ ‌
The‌‌reaction‌‌series‌‌also‌‌helps‌‌explain‌‌why‌‌certain‌‌minerals‌‌are‌‌only‌‌found‌‌in‌‌certain‌‌types‌‌of‌
igneous‌‌rocks.‌‌As‌‌olivine‌‌and‌‌pyroxene‌‌form‌‌at‌‌higher‌‌temperatures,‌‌they‌‌are‌‌more‌‌likely‌‌to‌‌be‌‌
found‌‌in‌‌ultramafic‌‌and‌‌mafic‌‌rocks,‌‌as‌‌compared‌‌to‌‌felsic‌‌rocks.‌‌Conversely,‌‌quartz‌‌is‌‌found‌‌
largely‌‌in‌‌felsic‌‌rocks‌‌due‌‌to‌‌forming‌‌at‌‌the‌‌lower‌‌temperatures‌‌and‌‌crystallizing‌‌later‌ ‌
‌
Picking‌‌a‌‌Field‌‌Guide‌ ‌
It‌‌is‌‌advisable‌‌to‌‌use‌‌a‌‌binder‌‌over‌‌a‌‌field‌‌guide,‌‌since‌‌not‌‌only‌‌can‌‌a‌‌binder‌‌be‌‌organized‌‌with‌‌
one’s‌‌own‌‌discretion,‌‌but‌‌also‌‌preparing‌‌sheets‌‌for‌‌a‌‌binder‌‌can‌‌help‌‌with‌‌learning‌‌facts‌‌(plus‌‌it‌‌
is‌‌great‌‌for‌‌general‌‌geology/petrology/mineralogy‌‌notes).‌‌However,‌‌for‌‌those‌‌who‌‌prefer‌‌field‌‌
guides,‌‌here‌‌is‌‌a‌‌guide,‌‌by‌‌a‌‌Science‌‌Olympiad‌‌veteran,‌‌on‌‌picking‌‌one:‌ ‌
Simon‌‌and‌‌Schuster‌‌‌-‌‌Definitely‌‌the‌‌best‌‌one‌‌of‌‌them‌‌all.‌‌Okay‌‌pictures,‌‌a‌‌lot‌‌of‌‌information,‌‌
and‌‌has‌‌great‌‌notes‌‌in‌‌the‌‌start‌‌of‌‌each‌‌section.‌‌I‌‌think‌‌it‌‌is‌‌quite‌‌concise‌‌and‌‌efficient‌‌-‌‌very‌‌
reliable.‌‌Not‌‌the‌‌easiest‌‌read,‌‌but‌‌definitely‌‌numero‌‌uno.‌‌Hands‌‌down‌ ‌
Peterson‌‌‌-‌‌A‌‌not-so-close‌‌second,‌‌but‌‌a‌‌clear‌‌silver‌‌medalist‌‌here.‌‌Not‌‌as‌‌informative‌‌as‌‌Simon‌‌
and‌‌Schuster,‌‌but‌‌does‌‌have‌‌nice‌‌pictures‌‌and‌‌good‌‌ID‌‌tips.‌‌I‌‌like‌‌the‌‌layout.‌‌Good‌‌backup‌ ‌
Audubon‌‌‌-‌‌This‌‌guide‌‌is‌‌pretty‌‌good,‌‌but‌‌rather‌‌unorganized.‌‌There‌‌is‌‌a‌‌lot‌‌of‌‌information,‌‌but‌‌a‌‌
lot‌‌of‌‌it‌‌is‌‌crammed‌‌too‌‌much‌‌and‌‌unimportant.‌‌The‌‌pictures‌‌are‌‌usually‌‌good,‌‌but‌‌the‌‌
information‌‌was‌‌a‌‌bit‌‌outdated‌‌even‌‌in‌‌the‌‌most‌‌recent‌‌version‌ ‌
Smithsonian‌‌‌-‌‌This‌‌one‌‌is‌‌great‌‌for‌‌learning‌‌how‌‌to‌‌identify‌‌the‌‌rocks,‌‌but‌‌once‌‌you‌‌get‌‌past‌‌
that,‌‌its‌‌use‌‌and‌‌value‌‌drops‌‌considerably.‌‌Not‌‌a‌‌terrible‌‌start,‌‌though‌ ‌
The‌‌Complete‌‌Guide‌‌to‌‌Rocks‌‌and‌‌Minerals‌‌‌-‌‌A‌‌bit‌‌similar‌‌to‌‌that‌‌of‌‌Smithsonian,‌‌but‌‌at‌‌least‌‌
goes‌‌a‌‌bit‌‌in‌‌depth.‌‌Seems‌‌quite‌‌large‌‌to‌‌carry‌‌around‌‌while‌‌running‌‌to‌‌stations‌‌-‌‌might‌‌as‌‌well‌‌
just‌‌use‌‌a‌‌binder‌ ‌
So,‌‌in‌‌short,‌‌if‌‌you’re‌‌just‌‌starting‌‌off,‌‌try‌‌Peterson‌‌or‌‌Smithsonian.‌‌Once‌‌you’ve‌‌mastered‌‌some‌‌
of‌‌the‌‌general‌‌basics,‌‌try‌‌your‌‌hand‌‌at‌‌Simon‌‌and‌‌Schuster.‌‌But‌‌why‌‌use‌‌them‌‌when‌‌you‌‌can‌‌
have‌‌a‌‌lovely‌‌binder?‌‌(Tip:‌‌it‌‌is‌‌perfectly‌‌okay‌‌to‌‌splice‌‌pages‌‌of‌‌your‌‌field‌‌guide‌‌into‌‌your‌‌binder)‌ ‌
‌