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Engineering Geology CVL 3315 Chapter 2 Matter and Minerals Dr. Sari Abusharar University of Palestine Faculty of Applied Engineering and Urban Planning Civil Engineering Department 2nd Semester 2014-2015 1 Outline of Presentation Minerals: Building Blocks of Rocks Atoms: Building Blocks of Minerals Why Atoms Bond Isotopes and Radioactive Decay Physical Properties of Minerals Mineral Groups Common Silicate Minerals Important Nonsilicate Minerals 2 Minerals: Building blocks of rocks Mineral, is defined as: • • • • Naturally occurring Inorganic solid substance Orderly crystalline structure Can be represented by a chemical formula Rock, is defined as: A solid aggregate or mass of minerals that occurs naturally as part of our planet Halite mineral Granite rock Composition of minerals Elements • Basic building blocks of minerals • Over 100 elements are known (92 naturally occurring) Atoms • Smallest particles of matter • Retains all the characteristics of an element 6 The Periodic Table Composition of minerals Atomic structure • Central region called the nucleus – Consists of protons (positive charges) and neutrons (neutral charges) • Electrons – Negatively charged particles that surround the nucleus – Located in discrete energy levels called shells Idealized structure of an atom Why Atoms Bond Chemical bonding الترابط الكيميائي Ionic bonding الترابط األيوني Covalent bonding الترابط التساھمي Metallic bonding الترابط الفلزي Why Atoms Bond Chemical bonding الترابط الكيميائي • Formation of a compound by combining two or more elements Ionic bonding الترابط األيوني • Atoms gain or lose outermost electrons to form ions • Ionic compounds consist of an orderly arrangement of oppositely charged ions Halite (NaCl) – An example of ionic bonding Why Atoms Bond Covalent bonding الترابط التساھمي • Atoms share electrons to achieve electrical neutrality • Covalent bonds are generally stronger than ionic bonds • Both ionic and covalent bonds typically occur in the same compound (bonds are seldom 100% ionic or covalent in character) Covalent bonding – sharing of valence electrons Formation of a covalent bond between two hydrogen atoms (H) to form a hydrogen molecule (H2) Covalent bonding in Diamond Diamond Why Atoms Bond Other types of bonding • Metallic bonding الترابط الفلزي – Valence electrons are free to migrate among atoms – Weaker and less common than ionic or covalent bonds – This type of bonding is found in metals such as copper, gold, aluminum, and silver Isotopes and Radioactive Decay Isotopes and radioactive decay النظائر واالضمحالل اإلشعاعي • Mass number is the sum of neutrons plus protons in an atom • Atomic number is the number of protons • An isotope is an atom that exhibits variation in its mass number (has same atomic number) • Some isotopes have unstable nuclei that emit particles and energy in a process known as radioactive decay Isotopes and Radioactive Decay Radioactive decay تحلل تلقائي ألنواع معينة من نويات الذرات إلى واحد أو أكثر من نويات عناصر أخرى ،وانطالق طاقة وجسيمات نووية ،مثل اضمحالل اليورانيوم – ٢٣٨إلى رصاص ، ٢٠٦-واضمحالل البوتاسيوم ٤٠-إلى أرجون.٤٠- Isotope ذرات عنصر لھا نفس العدد الذرى ،وتختلف فى أعداد الكتلة بسبب االختالف فى عدد النيترونات فى نواة العنصر . Isotopes and Radioactive Decay For example, carbon has three well-known isotopes. One has a mass number of 12 (carbon-12), another has a mass number of 13 (carbon13), and the third, carbon-14, has a mass number of 14. Carbon-12 must also have six neutrons to give it a mass number of 12. Carbon-14, on the other hand, has six protons plus eight neutrons to give it a mass number of 14. Physical properties of minerals Optical Properties LUSTER البريق COLOR اللون STREAK المخدش Crystal Shape or Habit الشكل البلوري Mineral Strength قوة المعدن HARDNESS الصالدة CLEAVAGE االنفصام FRACTURE المكسر Density and Specific Gravity Other Properties of Minerals Physical properties of minerals Primary diagnostic properties • Determined by observation or performing a simple test • Several physical properties are used to identify hand samples of minerals. Physical properties of minerals Luster … البريق درجة وشدة انعكاس الضوء من سطح معدن • Appearance of a mineral in reflected light • Two basic categories – Metallic فلزي – Nonmetallic الفلزي • Other terms are used to further describe luster such as vitreous زجاجي, silky حريري, or earthyترابي Galena is a lead sulfide (PbS) كبرتيد الرصاصthat displays metallic luster The freshly broken sample of galena (right) displays a metallic luster, while the sample on the left is tarnished ()ملوث and has a submetallic luster. Quartz,consists of silica, or silicon dioxide (SiO2), that displays vitreous luster Physical properties of minerals Color • Generally an unreliable diagnostic property to use for mineral identification • Often highly variable for a given mineral due to slight changes in mineral chemistry • Exotic colorations of some minerals produce gemstones Quartz (SiO2) exhibits a variety of colors These samples include: • crystal quartz (colorless) , • amethyst (purple quartz) • citrine (yellow quartz) • smoky quartz (gray to black). Malachite, Sulfur, and Azurite exhibits a variety of colors Sulfur (bright yellow) الكبريت Azurite (deep blue ) الالزورد Malachite (bright green) Cu2CO3(OH)2 المليكيت Sulfur: used for Explosives صناعة المتفجرات Fungicides مبيد الفطريات Fertilizers سماد طبيعي أو كيميائي Realgar زرنيخ أحمرused for arsenic and to give fireworks the red color Physical properties of minerals Streak المخدش • Color of a mineral in its powdered form • Helpful in distinguishing different forms of the same mineral ويحصل عليه بحك المعدن بسطح، • لون مسحوق المعدن . خشن صلب A mineral’s streak is obtained by rubbing it across a streak plate (a piece of unglazed porcelain) and observing the color of the mark it leaves. Although the color of a mineral is not always helpful in identification, the streak can be very useful. Crystal Shape or Habit ھيئة البلورة Mineralogists (expert in the properties and character of minerals ) use the term crystal shape or habit to refer to the common or characteristic shape of a crystal or aggregate of crystals. Some common crystal habits A. Bladed. Elongated crystals that are flattened in one direction. B. Prismatic. Elongated crystals with faces that are parallel to a common direction. نصلية الشكل منشوري C. Banded. Minerals that have stripes or bands of different color or texture. D. Botryoidal. Groups of intergrown crystals resembling a bunch of grapes. شريطية عنقودي Physical properties of minerals Hardness الصالدة • Resistance of a mineral to abrasion or scratching • All minerals are compared to a standard scale called the Mohs scale of hardness وتقاس الصالدة على مقياس. • درجة مقاومة المعدن للكسر أو الخدش ( أقلھا صالدة بينما يمثل رقم١) موھز الذى يشمل عشر درجات يمثل رقم (٢) talc ( تلك١) : وھى مرتبة كالتالى. ( أكثر المعادن صالدة١٠) (٥) fluorite ( فلوريت٤) calcite ( كالسيت٣) gypsum جبس quartz ( كوارتز٧) orthoclase ( أورثوكالز٦) apatite أباتيت ( الماس١٠) corundum ( كورندم٩) topaz ( توباز٨) . diamond Mohs scale of hardness • This property is determined by rubbing a mineral of unknown hardness against one of known hardness, or vice versa. • It should be noted that the Mohs scale is a relative ranking, and it does not imply that mineral number 2, gypsum, is twice as hard as mineral 1, talc. In fact, gypsum is only slightly harder than talc. Physical properties of minerals Cleavage اإلنفصام على امتداد أسطح مستويات ذات، ميل المعدن للتكسر في اتجاھات مفضلة الروابط الضعيفة ..الضعيفة • Tendency to break along planes of weak bonding • Produces flat, shiny surfaces • Described by resulting geometric shapes – Number of planes – Angles between adjacent planes Cleavage in Muscovite Mica The thin sheets shown here were produced by splitting a mica (muscovite) crystal parallel to its perfect cleavage. Common cleavage directions When minerals break evenly in more than one direction, cleavage is described by the number of cleavage directions and the angle(s) at which they meet. مسكوفيت الفلسبار ھورنبلند Common cleavage directions ھاليت كالسيت معين األوجه فلوريت Three examples of perfect cleavage – fluorite, halite, and calcite fluorite halite calcite Physical properties of minerals المكسرFracture • Absence of cleavage when a mineral is broken • التكسير غير المنتظم للبلورة عبر أسطح ال توازى وجه البلورة ،وتستخدم للتفرقة بين المعادن . مكسر محاري Conchoidal fracture تعنى حرفيا "مثل الصدفة” ،وھو وصف لشكل مكسر بعض )مثل والمعادن الصخور األوبسيديان والكوارتز( ،والتى تأخذ شكل أسطح بھا نتوءات منحنية متحدة المركز . The smooth curved surfaces result when minerals break in a glasslike manner. Physical properties of minerals Density الكثافة • An important property of matter, is defined as mass per unit volume. Physical properties of minerals Specific Gravity • Ratio of the weight of a mineral to the weight of an equal volume of water • Most minerals are between 2 and 3. • Average value is approximately 2.7 • Quartz has a specific gravity of 2.65 • Galena, an ore of lead, has a specific gravity of roughly 7.5 • 24-karat gold is approximately 20 Physical properties of minerals Other properties • • • • • • • Magnetism المغناطيسية Reaction to hydrochloric acid Malleabilityقابلية التطريق Double refraction Taste Smell Elasticity المغناطيسية Magnetism Reaction to hydrochloric acid One very simple chemical test involves placing a drop of dilute hydrochloric acid on a freshly broken mineral surface. Using this technique, certain minerals, called carbonates, will effervesce يفور (fizz) as carbon dioxide gas is released Calcite reacting with a weak acid Double refraction illustrated by the mineral calcite. some minerals exhibit special optical properties. For example, when a transparent piece of calcite is placed over printed text, the letters appear twice. This optical property is known as double refraction. Mineral Groups Nearly 4000 minerals have been identified (named) and several new ones are identified each year. Rock-forming minerals • Common minerals that make up most of the rocks of Earth’s crust • Only a few dozen are abundant! • Composed mainly of the 8 elements that make up over 98% (by weight) of the continental crust Relative abundance of the eight most abundant elements in the continental crust Mineral Groups Silicates • Most important mineral group – Comprise most of the rock-forming minerals – More than 800 silicate minerals are known – they account for more than 90 percent of Earth’s crust. – Very abundant due to large amounts of silicon and oxygen in Earth’s crust • silicon-oxygen tetrahedron molecule – Fundamental building block – Four oxygen ions surrounding a much smaller silicon ion Silicate structures Two representations of the silicon–oxygen tetrahedron. A. The four large spheres represent oxygen ions, and the blue sphere represents a silicon ion. The spheres are drawn in proportion to the radii of the ions. B. An expanded view of the tetrahedron that has an oxygen ion at each of the four corners. Mineral Groups Joining Silicate structures • Single tetrahedra are linked together to form various structures including: – Independent tetrahedra – Single chain – Double chain – Sheet structure – Three-dimentional framework Silicate structures The relative sizes and charges of ions commonly found in minerals Ionic radii are usually expressed in angstroms (1 angstrom equals 10-8cm) Mineral Groups The Light Silicates Or nonferromagnesian. Generally light in color and specific gravity of about 2.7 Nonferromagnesian minerals )ﺘﺤﺘوي.ﻤﻌﺎدن ﺴﻴﻠﻴﻜﺎﺘﻴﺔ ﻤﻜوﻨﺔ ﻝﻠﺼﺨور ﻻ ﺘﺤﺘوى ﻋﻠﻰ اﻝﺤدﻴد واﻝﻤﺎﻏﻨﺴﻴوم (........ ﻜﺎﻝﺴﻴوم، ﺼودﻴوم،ﺒوﺘﺎﺴﻴوم Mineral Groups Common Silicate minerals • Light silicates: Feldspar Group – Most common mineral group – 50 percent of Earth’s crust. – 3-dimensional framework of tetrahedra exhibit two directions of perfect cleavage at 90 degrees – Orthoclase ( األورثوكليزpotassium feldspar) and Plagioclase ( البالجيوكليزsodium and calcium feldspar) are the two most common members Common Silicate Minerals Orthoclase feldspar Plagioclase feldspar These parallel lines, called striations ()حزوز, are a distinguishing characteristic of plagioclase feldspar. Mineral Groups Common Silicate minerals • Light silicates: Quartz (SiO2) الكوارتز –Only common silicate composed entirely of oxygen and silicon –Hard and resistant to weathering –Conchoidal fracture –Often forms hexagonal crystals Common Silicate Minerals Mineral Groups Common Silicate minerals • Light silicates: Muscovite –Common member of the mica family –Excellent cleavage in one direction –Produces the “glimmering” brilliance لمعانoften seen in beach sand Common Silicate Minerals Dark silicates Light silicates Mineral Groups Common Silicate minerals • Light silicates: Clay minerals – Clay is a general term used to describe a variety of complex minerals – Clay minerals all have a sheet or layered structure – Most originate as products of chemical weathering The Dark Silicates Or ferromagnesian, contains ions of iron=ferro and/or magnesium. Because that content they are dark in color and have a greater specific gravity. Ferromagnesian minerals ﻤﻌﺎدن اﻝﻔﻴروﻤﻐﻨﻴﺴﻴﺔ . أو اﻝﻤﺎﻏﻨﺴﻴوم/ﻤﻌﺎدن ﺴﻴﻠﻴﻜﺎﺘﻴﺔ ﻤﻜوﻨﺔ ﻝﻠﺼﺨور ﺘﺤﺘوى أﺴﺎﺴﺎ ﻋﻠﻰ اﻝﺤدﻴد و وﻴﺴﺘﺨدم ﻫذا اﻻﺴم ﻝوﺼف اﻝﻤﻌﺎدن اﻝﺸﺎﺌﻌﺔ ﻤﺜل اﻷوﻝﻴﻔﻴن واﻝﻬﺒرﺴﺜﻴن اﻷوﺠﻴت . واﻝﻬورﻨﺒﻠﻨد واﻝﺒﻴوﺘﻴت Mineral Groups Common Silicate minerals • Dark silicates: Olivine group – a family of high-temperature silicate minerals – black to olive green in color and have a glassy luster and a conchoidal fracture – Individual tetrahedra linked together by iron and magnesium ions – Forms small, rounded crystals with no cleavage Common Silicate Minerals Mineral Groups Common Silicate minerals • Dark silicates: Pyroxene Group – Single chain structures involving iron and magnesium – Two distinctive cleavages at nearly 90 degrees – Augite is the most common mineral in the pyroxene group Common Silicate Minerals Mineral Groups Common Silicate minerals • Dark silicates: Amphibole Group – Double chain structures involving a variety of ions – Two perfect cleavages exhibiting angles of 120 and 60 degrees – Hornblende is the most common mineral in the amphibole group Common Silicate Minerals Cleavage angles for augite and hornblende Mineral Groups Common Silicate minerals • Dark silicates: Biotite –iron-rich member of the mica family –Excellent cleavage in one direction - Like hornblende, biotite is a common constituent of igneous rocks, including the rock granite. Common Silicate Minerals Dark silicates Light silicates Mineral Groups Important nonsilicate minerals Typically divided into classes based on anions Comprise only 8% of Earth’s crust Often occur as constituents in sedimentary rocks Mineral Groups Important nonsilicate minerals • Several major groups exist including – Oxides – Sulfides – Sulfates – Native Elements – Carbonates – Halides Mineral Groups سماد األصباغ خام الحديد يستعمل للصنفرة Mineral Groups Mineral Groups Important nonsilicate minerals • Carbonates – Primary constituents in limestone and dolostone حجر الدولوميت – Calcite (CaCo3, calcium carbonate) and Dolomite (Ca,Mg(CO3)2, calcium-magnesium carbonate) are the two most important carbonate minerals Mineral Groups Important nonsilicate minerals • Many nonsilicate minerals have economic value • Examples – Hematite (oxide mined for iron ore) – Halite (halide mined for salt) – Sphalerite (sulfide mined for zinc ore) – Native Copper (native element mined for copper) – Gypsum (sulfate mined for sheetrock اللوح الجصي, etc.) Estimated percentages (by volume) of the most common minerals in Earth’s crust. End of Chapter 2