Minerals Definition, Types, and Identification Forensic Applications

Niocalite (blue) in sovite (calcite + Transparent emerald, the apatite). Oka carbonatite complex.

green variety of beryl, on Crossed-polars. Width = 5.4 mm

calcite matrix Department Environmental, Earth, & Atmospheric Sciences Earth, & Atmospheric Department Environmental, Department Environmental, Earth, & Atmospheric Sciences • • • • • • Rocks areaggregates ofoneormoreminerals Minerals areeverywhere Building blocksofrocks, soil,dirt,andmud Rocks areaggregates ofoneormoreminerals Minerals areeverywhere Building blocksofrocks, soil,dirt,andmud Fluorite Minerals Minerals Gneiss Department Environmental, Earth, & Atmospheric Sciences 4. 3. 2. 1. 4. 3. 2. 1. certain limits Chemical composition fixedor varieswithin Crystalline regular way i.e., atomsinthemineral arearrangedina Inorganic Naturally Occurring certain limits Chemical composition fixedor varieswithin Crystalline regular way i.e., atomsinthemineral arearrangedina Inorganic Naturally Occurring – – Mineral Definition Mineral Definition has adefiniteinternal structure, has adefiniteinternal structure, Department Environmental, Earth, & Atmospheric Sciences • • • • Inorganic Naturally Occurring Inorganic Naturally Occurring as: Ivory,Amber,Coal, Pearls that waseveralive.Therefore, materialssuch rubies andemeralds don naturally as: Ivory,Amber,Coal, Pearls that waseveralive.Therefore, materialssuch rubies andemeralds don naturally - - - - minerals arenotformed byanything minerals arenotformed byanything glass, concrete,synthetic diamonds, glass, concrete,synthetic diamonds, Minerals Minerals - - minerals mustbeformed minerals mustbeformed ’ ’ t count t count are notminerals! are notminerals! Department Environmental, Earth, & Atmospheric Sciences • • definite structurethat controlstheirproperties. orderly atomicarrangement givingthema definite structurethat controlstheirproperties. orderly atomicarrangement givingthema Crystalline Crystalline Graphite - - the atomsinminerals havean the atomsinminerals havean Minerals Minerals Diamond Department Environmental, Earth, & Atmospheric Sciences • • Halite = NaCl different chemistryform differentminerals. compounds withthe samestructurebut varies withincertain limits. Crystalline different chemistryform differentminerals. compounds withthe samestructurebut varies withincertain limits. Crystalline Chemistry Chemistry - - Chemical composition isfixedor Chemical composition isfixedor Minerals Minerals Cubic array of atoms Sylvite = KCl Department Environmental, Earth, & Atmospheric Sciences packed aroundaparticularcation. determines thenumberofanions thatcanbe ratio =sizecation/sizeanion. The radiusratio andcalculatethe radius perspective ofthecation packing. Weusuallylookatthis fromthe their relativesizes.Thisisreferred toasclosest Ions arearrangedincrystalstructures accordingto Structure ofMinerals Structure of Minerals

Crystal Lattice: the three dimensional molecular structure of a mineral. (Shape of the “unit

cell.”)

• Various ions make up the mineral. • Geometry + chemistry! Department Environmental, Earth, & Atmospheric Sciences Earth, & Atmospheric Department Environmental,

StructureStructure ofof mineralsminerals Polymorphs

• Minerals with the same composition but different crystalline structures • Examples include diamond and graphite • Phase change – one polymorph changing into another Diamond Graphite Department Environmental, Earth, & Atmospheric Sciences Earth, & Atmospheric Department Environmental, PhysicalPhysical propertiesproperties ofof mineralsminerals CrystalCrystal FormForm • External expression of a mineral’s internal

structure • Often interrupted due to competition for space and rapid loss of heat

Crystals are the smallest “bits” of minerals and reflect the geometry of the mineral molecules molecules Department Environmental, Earth, & Atmospheric Sciences Earth, & Atmospheric Department Environmental, PhysicalPhysical propertiesproperties ofof mineralsminerals ColorColor • Generally unreliable for mineral identification • Often highly variable due to slight changes in mineral chemistry • Exotic colorations of certain minerals produce gemstones • Some minerals are used as pigments

Quartz (SiO2)

exhibits a variety of colors of colors Department Environmental, Earth, & Atmospheric Sciences Earth, & Atmospheric Department Environmental, PhysicalPhysical propertiesproperties ofof mineralsminerals

StreakStreak Color of a mineral in its powdered form

Streak is obtained on an unglazed porcelain plate porcelain plate Department Environmental, Earth, & Atmospheric Sciences Earth, & Atmospheric Department Environmental, PhysicalPhysical propertiesproperties ofof mineralsminerals

LusterLuster • Appearance of a mineral in reflected light • Two basic categories • Metallic • Nonmetallic • Other descriptive terms include vitreous, silky, or earthy

Galena (PbS) displays metallic luster metallic luster Department Environmental, Earth, & Atmospheric Sciences Earth, & Atmospheric Department Environmental, PhysicalPhysical propertiesproperties ofof mineralsminerals

Hardness • The hardness of a mineral is its resistance to

scratching. • The standard scale for

measuring hardness is Moh’s Hardness scale. Hardness scale. Department Environmental, Earth, & Atmospheric Sciences Earth, & Atmospheric Department Environmental, PhysicalPhysical propertiesproperties ofof mineralsminerals CleavageCleavage • Tendency to break along planes of weak bonding • Produces flat, shiny surfaces • Described by resulting geometric shapes • Number of planes • Angles between adjacent planes

Fluorite, halite, and calcite all exhibit perfect perfect cleavage Department Environmental, Earth, & Atmospheric Sciences Earth, & Atmospheric Department Environmental,

CleavageCleavage

Due to planes of weakness caused by alignment of the common crystal faces of the common crystal faces Department Environmental, Earth, & Atmospheric Sciences Earth, & Atmospheric Department Environmental, Department Environmental, Earth, & Atmospheric Sciences PhysicalPhysical propertiesproperties ofof mineralsminerals FractureFracture • Absence of cleavage when a mineral is broken SpecificSpecific GravityGravity • Weight of a mineral / weight of an equal volume of water • Average value = 2.7 OtherOther propertiesproperties Magnetism Reaction to hydrochloric acid Malleability Double refraction Taste Smell

Elasticity

Elasticity Department Environmental, Earth, & Atmospheric Sciences Earth, & Atmospheric Department Environmental, Department Environmental, Earth, & Atmospheric Sciences Halides Sulfates ugtts& molybdates & tungstates vanadates, chromates, Phosphates, arsenates, Silicates Oxides elements Native Sulfides Hydroxides Carbonates Class classes Mineral 7-1. Table Borates Metals in combination with hydroxyls (OH hydroxyls with combination in Metals ZO uft SO ( sulfate with metals combination in orAlkaline earths tetrahedra isolated and chains sheets, networks, (CO combination with halogens (F, Cl, Br, I) earths metalsin or alkaline Alkali uft SO ( sulfate Chemical characteristics Chemical (As, Se, Te) Se, (As, One or more metals in combination with combination metals more in or One (SiO with combination in Metals element or ametallic nonmetallic of compound Pure reduced sulfur or chemically similar elements similar or sulfur chemically reduced with combination metals more in or One (CO carbonate with combination in Metals (SiO silica tetrahedra with combination in Metals earths metalsin or alkaline Alkali Metals in combination with carbonate with combination in Metals Alkaline earths or metals in combination with metals combination in orAlkaline earths Metals in combination with silica tetrahedra with combination in Metals Various elements in combination with the in combination elements Various Various elements in combination with boron Borax [Na Borax with boron in combination elements Various 4 radical where Z = P, As, V, Cr, W, Mo W, Cr, V, As, P, = Z where radical 3 4 2 4 & & ) ) forming three dimensional forming ) 4 2 & ) - ) Brucite [Mg(OH) Fluorite [CaF Apatite [Ca Scheelite [CaWO Scheelite Skutterudite [CoAs Forsterite [MgSiO Forsterite Pyrite [FeS Hematite [FeHematite Quartz [SiO Orthoclase [KAlSi Halite [NaCl] Epsomite [MgSO Epsomite Galena [PbS] Cerrusite [PbCO Barite [BaSO Carnotite [K Examples Graphite [C] Gold [Au] Calcite [CaCO 2 2 B 5 2 ] (PO 2 ] 4 3 (UO 2 4 O O ] ] 3 4 ] 7 4 ] @ 3 10H ) 4 2 ] 4 2 3 4 ] ] @ 3 (VO (F,Cl,OH ] 7H 3 O ] 8 2 ] O] 2 O] 4 ) 2 @ 3 H ) Department Environmental, Earth, & Atmospheric Sciences the silicatetrahedron. block forthesilicateminerals is minerals. Thebasicbuilding the Earth’scrustaresilicate The mostcommonmineralsin Department Environmental, Earth, & Atmospheric Sciences Nesosilicate Independent tetrahedra Independent Nesosilicate hloiiaeSeto erhdasaigtrecres3Si 3 three sharing corners of tetrahedra Sheet Phyllosilicate two sharing tetrahedra of chain Single Inosilicate two sharing more tetrahedra or Three a corner sharing tetrahedra Two Cyclosilicate Sorosilicate et sl ct Framework of tetrahedraTektosilicate sharing all four Class classes crystal ofsilicate the Properties 7-4. Table corners sharing two three corners two or sharing corners ring a forming corners, Double chain of tetrahedra alternately tetrahedra of chain Double Tetrahedral arrangement Tetrahedral # shared corners . Si 2.5 4 2 2 SiO 0 1 h mical Che SiO SiO Si Si SiO SiO Si SiO SiO Si 2 4 2 unit O O O 3 3 4 2 3 3 4 5 11 7 2 6 6 & & & & & & 1:2 1:2.5 Hornblende 1:2.75 Augite 1:3 Beryl 1:3 Melilite Olivine 1:3.5 1:4 Si:O K-feldspar Example Department Environmental, Earth, & Atmospheric Sciences Quartz (SiO common componentsof soil. Madrid Basin, Spain. showing arose liketexture, Miocene arkose, 2 ) andtheclaymineralsare themost Clay Minerals Department Environmental, Earth, & Atmospheric Sciences gibbsite. Al3+ can substitute for Si4+ in the tetrahedral layer. octahedral layer =brucite. Al3+ inthe octahedral layer = Structure of the octahedral and tetrahedral layer. Mg2+ inthe Clay mineralsarebuiltby combining tetrahedral andoctahedral layers. Department Environmental, Earth, & Atmospheric Sciences iueaisSacl oul edl takdAttacked attacked Readily soluble Scarcely Heating 200 acids Dilute Formula capacity (CEC) in exchange Cation groups mineral clay layered the of characteristics principal of the Summary 7-5. Table Basal spacing 7.1 7.1 spacing Basal Interlayer water Only in Some in Some halloysite in Only water Interlayer Nil cations Interlayer Octahedral layer Di-octahedral Mostly Mostly di- Di-octahedral layer Octahedral Octahedral Tetrahedral: Structure Examples Kaolinite, , Kaolinite, Examples meq/100 g clay g meq/100 Ethylene glycol Only Only taken by up Ethylene glycol o Except halloysite, C unchanged Al 3 - 15 Nil art h lloysite , ha halloysite little variation 1:1 2 Si D 2 O 5 (OH) 2 , No marked change Collapse to Collapse marked change No celadonite O 10 10 -10 40 Low , brammallite, , hydrous No effect No K hydromuscovite octahedral 2:1 K , phengite, micas, 10 0.5-0.75 D (OH) Al 2 2 (Si,Al) 2 approximately 10 approximately hectorite, , , beidellite, Montmorillonite, Smectites sauconite D (Si,Al) M H 80 -80 150 High 17 17 layers, glycol Two layers Na, one manyto Ca, two layers octahedral tri- or Di- 2:1 Ca, Na Ca, most ~15 ~15 most Variable 2 + O 0.7 D (Y 8 O 3+ ,Y 20 D OH) (O 2+ ) 4-6 4 @ n spacing layer of shrinkage 14.4 (Si,Al) 14 glycolOne layer, M H 100 - 100 - 150 High hydrated K, one layer to nil layer one K, two Ca, layers octahedral tri- Mostly 2:1 Mg Readily attacked Readily Exfoliation, Variable miculites Ver e miculite Ver 2 2+ O D 0.66 D (Y 8 when fully O 2+ 20 , Y OH) (O 3+ ) 4 6 @ 8 Department Environmental, Earth, & Atmospheric Sciences Structure of kaolinite a 1:1 layerclay a Structure ofkaolinite O T T occupied. octahedral layerare octahedral sitesinthe only twooutofthree tetrahedral layer.Notethat gibbsite layeranda structural unitconsistsofa Structure ofkaolinite.Each Department Environmental, Earth, & Atmospheric Sciences Saponite Sauconite Montmorillonite Mineral Hectorite Nontronite Beidellite Table 7-6. Substitutions for smectite group mineralsclay Tetrahedral cations Tetrahedral Si Si Si Si Si Si 6.7 8 7.2 7.3 7.3 8 Al Al Al Al 1.3 0.8 0.7 0.7 Tri-octahedral Di-octahedral Octahedral cations Zn Mg Mg Al Al Fe 4 3.3 4-6 4 3 5.3 6 % Mg (Mg,Al,Fe Li 0.7 0.7 3+ ) 2-0 (0.5Ca,Na) (0.5Ca,Na) (0.5Ca,Na) (0.5Ca,Na) (0.5Ca,Na) (0.5Ca,Na) Exchangeable cations Exchangeable 0.7 0.7 0.8 0.7 0.7 0.7 Department Environmental, Earth, & Atmospheric Sciences tutr fmnmrloiea2:1layerclay Structure ofmontmorillonite IL O T T T interlayer position. (exchangeable cations)inthe Mg a gibbsitelayer.Substitutionof 2:1 clay.Theoctahedrallayeris Structure ofmontmorillonite,a addition ofNa layer ischargebalancedbythe 2+ for Al 3+ in theoctahderal + or Ca 2+ cations Department Environmental, Earth, & Atmospheric Sciences Stereomicroscope Tools forIdentification andCharacterizationof SEM Minerals PLM EMP XRD Department Environmental, Earth, & Atmospheric Sciences andtexture Stereomicroscopy Carbonate sand Stream sand Beach sand Department Environmental, Earth, & Atmospheric Sciences Polarizing Light Microscopy (PLM) – a forensicworkhorse a Polarizing LightMicroscopy(PLM)– mounting media orindex oil. lower refractive indexthen the determine ifmaterialhas ahigheror linemethodis usedto The Becke or indexoil. index relativetothemountingmedia Higher reliefmeanshigherrefractive Use various optical propertiesto Use various characterize materials Index ofrefraction Department Environmental, Earth, & Atmospheric Sciences Polarizing Light Microscopy (PLM) – a forensicworkhorse a Polarizing LightMicroscopy(PLM)– iernec oo hne ne rse-oasduetoretardation color changesundercrossed-polars Birefringence – Pleochroism Plane polarized light oo hne ssaei oae polarizedlight changesasstageisrotated– color – Crocidolite Crossed-polars Department Environmental, Earth, & Atmospheric Sciences act rhombohedral Calcite - Polarizing Light Microscopy (PLM) – a forensicworkhorse a Polarizing LightMicroscopy(PLM)– Dynel Morphology and“habit” Fiber characteristics Biotite flake Dog’s hair Human hair(mongoloid) rcdlt fiber Crocidolite Department Environmental, Earth, & Atmospheric Sciences identify thematerial. diffraction andtheintensityof diffractedwavelengthscanbeusedto for Law (aNobelprizeforsimpletrigonometry). Theanglesrequired A powerfulwaytoidentifycrystalline materials.ThephysicalbasisisBragg’s X-ray diffractometer X-ray Diffraction(XRD) spacing. law conditions aremet. of incidence and diff Diagram illustrating Bragg’s law. raction whenBragg’s d = inter-planar = inter-planar 2 = angle Department Environmental, Earth, & Atmospheric Sciences ray powderdiffractometer. Configuration foratypicalX- Department Environmental, Earth, & Atmospheric Sciences Mineral X-raydiffraction patterns Department Environmental, Earth, & Atmospheric Sciences determined. elemental abundances can be darker. Using EDAX, quantitative lower atomic numberelements are number of theelements.Areas with shades are relatedtothe atomic first atomicbomb wasdetonated.The desert sandatAlamogordo whenthe tinitite, theglass formedfromthe The materialillustrated hereis Scanning ElectronMicroscopy(SEM)withEDAX Can beusedtocharacterizematerials atthemicronlevel. Back scatter electron image Department Environmental, Earth, & Atmospheric Sciences data wouldbeuseful. small asonemicronindiameter. Theremaybespecificcaseswheresuch be usedtodeterminetheabundance of butitcan This instrumentisnotcommonly usedinforensicinvestigations, The ElectronMicroprobe (EMP) a varietyofelementsonareasas 1 microndiameterspots. carbonatite. Analysesweredone on Rare-earth carbonatemineralsin Department Environmental, Earth, & Atmospheric Sciences Frankfurt, Germany When Disch strangled bodyofEva In Octoberof1904the coal hornblende, snuff and, contained bits of at thescene that filthy handkerchief found called inhe examineda Frankfurt, Germany When Disch strangled bodyofEva In Octoberof1904the coal hornblende, snuff and, contained bits of at thescene that filthy handkerchief found called inhe examineda was foundnear was foundnear First ForensicGeology Case Georg Georg First ForensicGeology Case Popp was Popp was Department Environmental, Earth, & Atmospheric Sciences bearing rocks that hadhornblende works andataquarry at themurder scene trousers thatmatched mica inthe cuffs ofhis The suspect alsohad coal used snuff,workedat the A suspect,Karl bearing rocks that hadhornblende works andataquarry mica at themurder scene trousers thatmatched mica inthe cuffs ofhis The suspect alsohad coal used snuff,workedat the A suspect,Karl - - First ForensicGeology Case burning localgas First ForensicGeology Case burning localgas Laubach Laubach , , Department Environmental, Earth, & Atmospheric Sciences (thanks toRay short distance downstream. minerals were notfounda up stream.The softcopper abandoned copper mine just Malachite and Azuritefroman crossing. Samples contained the crimesceneatariver compared withsoilfrom Suspect Evidence Crime Location: FrontRoyal,Va (thanks toRay short distance downstream. minerals were notfounda up stream.The softcopper abandoned copper mine just Malachite and Azuritefroman crossing. Samples contained the crimesceneatariver compared withsoilfrom Suspect Evidence Crime Location: FrontRoyal,Va : Homicide : Homicide ’ ’ s vehicle s vehicle : Soilonthe : Soilonthe Murary Murary Junger Junger ) ) . . Case Case Department Environmental, Earth, & Atmospheric Sciences snow and ice. it for use inthe control of section ofhighway totest been spread on asmall furnace slag thathad the sandwas blast investigation showedthat murder scene. Geologic suspects car, andatthe found onthevictim, in a peculiar blacksandwas Washington, D.C.A Anacostia at theedgeof woman In Septemberof1958 a snow and ice. it for use inthe control of section ofhighway totest been spread on asmall furnace slag thathad the sandwas blast investigation showedthat murder scene. Geologic suspects car, andatthe found onthevictim, in a peculiar blacksandwas Washington, D.C.A Anacostia at theedgeof woman In Septemberof1958 a (Block, 1979 p.149 (Block, 1979 p.149 ’ ’ s bodywasfound s bodywasfound The ReevesMurder Case The ReevesMurder Case River in River in - - 152) 152) SandSand fromfrom aa ConstructionConstruction SiteSite

In another example, in southern Ontario a man was arrested and charged with the beating death of the young girl. The scene of the crime was a construction site adjacent to a newly poured concrete wall. The soil was sand that had been transported to the scene for construction purposes. As such, the sand had received additional mixing during the moving and construction process and was quite distinctive. The glove of the suspect contained sand that was similar to that found at the scene and significantly different in composition and particle size from the area of the suspect’s home. This was important because the suspect claimed the soil on the gloves came from his garden. (Murray and Tedrow, 1992 , p. 16) Department Environmental, Earth, & Atmospheric Sciences Tedrow foundry. suspect hadbeen atthe shoes indicated thatthe Canada the sandonthe found inplace inthatpartof Because olivine sandisnot had grains ofolivinesand Canada asuspect case atafoundryinToronto, In abreakingandentering in foundrywork olivine, zircon,etc.are used Sands ofheavyminerals, Tedrow foundry. suspect hadbeen atthe shoes indicated thatthe Canada the sandonthe found inplace inthatpartof Because olivine sandisnot had grains ofolivinesand Canada asuspect case atafoundryinToronto, In abreakingandentering in foundrywork olivine, zircon,etc.are used Sands ofheavyminerals, Commercial Foundry Sand Commercial Foundry Sand , 1992 ,p. 79) , 1992 ,p. 79) (Murray and (Murray and ’ ’ s shoes s shoes Department Environmental, Earth, & Atmospheric Sciences Geochemistry. Thomson. Eby, G.N.(2004) PrinciplesofEnvironmental Other tablesandgraphics arefrom: Illinois University were graciouslyprovided byJackCrelling,Southern Case studiesandsomeof thegraphicsusedinthistalk Acknowledgements