EAR 105 1st Edition Lecture 4Outline of Last Lecture I. Constituency of the Earth—continueda. By compositionb. By behavior (rheology)II. Plate TectonicsIII. Continents & Ocean BasinsOutline of Current Lecture IV. Intro to MineralsV. Atomic Structure of MineralsVI. Mineral DiagnosticsVII. Natural ResourcesCurrent LectureIV. Intro to Minerals- Minerals are the fundamental building block of rocks.- They construct the built environment.- They are important to human health & environment.- Minerals: (1.) Naturally occurring (2.) inorganic (3.) crystalline (4.) solids (5.) with a specific chemical composition/ with a set range of chemical componentso (I.e. Ice is considered a mineral, whereas liquid water is not, since the latter doesn’t meet the 4th specification of a mineral.)- Rocks: aggregates of one or more minerals or mineral-like substanceso (Ex. Granite is an aggregate of feldspar, hornblende, and quartz.V. Atomic Structure of Minerals- Minerals are compounds of combined elements.- Elements: formed of 1 or more of the same type of atom—defined by number of protons in the nucleuso Over 100 different elements are known- Atoms: formed of protons (positively charged) and neutrons (neutrally charged) in the nucleus (center) of the atom.o Electrons: small negatively charged particles that hover around the nucleus in what is known as an electron cloud. Electronsoccupy specific energy levels (aka electron shells) in the electron cloud. It is the outermost layer of electrons, known as the valence electrons that form bonds. According to the Octet Rule, the valence electron shell aims to gain the ideal, or full, capacity of 8 valence electrons.- The Octet Rule gives a clue as to the propensity of certain elements to bond—the closer the element is to having a full valence layer, the less likely it is to react, in general. Similarly, an element whose valence layer contains 7 electrons will most likely bond with an element whose valence layer contains 1 electron, reaching a sum of the maximum 8 valence electrons.- Thus, as atoms bond to reach an ideal valence layer of 8 electrons, they form elements are minerals.- Atoms bonds generally cause the particle to be more neutral and stable.- There are three types of atomic bonds—two of them are highlighted for the purposes of this class: Ionic, Covalent, and Metallic.o Ionic Bonds: occur when valence electrons are transferred between atoms. This is generally the weakest type of bond. Ions are atoms with a positive or negative charge. Thus, ionic bonds form when ions of opposite charges attract.o Covalent Bonds: occur when valence electrons are shared between atoms. This is a generally stronger type of bond.o Metallic bonds occur when metals’ valence electrons are free to flow throughout the entire structure—not emphasized in EAR 105 thus far.- Most minerals in the Earth’s crust are silicate minerals, meaning they have a high content of the mineral silica- Silica is a mineral made of the elements Silicon and Oxygen (SiO4) joined togetherin a very strongcovalent bond! Yay!o In detail: a singular silicon atom is surrounded by 4 Oxygen atoms, forming what is known as the silicate tetrahedron.o The silica tetrahedron is the building block of most minerals. The mineral quartz is made exclusively of silica. To reiterate, silica is formed of very strong covalent bonds, making quartz among themost resilient minerals when put to the test of weathering.  Silica tetrahedrons can bond to take on various forms, which in turn defines the crystal shape (habit) of the mineral produced.- Ex. sheet silicates, chain silicates, double chain silicates- For more or less complex reasons, the atomic structure of a mineral is indicative of its physical properties. - Mineral Groups:Eight elements compose most rock-forming minerals.o Oxygen (O),o Silicon (Si),o Aluminum (Al)o Iron (Fe)o Calcium (Ca)o Sodium (Na)o Potassium (K)o Magnesium (Mg)VI. Mineral Diagnostics- The term mineral diagnostics relates to the identification of minerals based on itsvarious properties.- Color and streak: can relate to the visual coloration of the mineral, but since this quality may be skewed by slight impurities in the mineral composition, the streak, defined by the color of the trace left by a mineral when rubbed across a porcelain plate, bears much more significance in determined the type of mineral.- Luster: Relates to the quality of shine attributed to a mineral. Some descriptive categories include metallic, submetallic, or nonmetallic, the latter category then being qualified as vitreous (glassy), silky, greasy, earthy, pearly, dull etc.o Ex. Galena has a metallic luster when freshly mined, but tarnishes when exposed to the atmosphere, changing its luster to submetallic.- Crystal Shape: relates to the typical shape taken by individual or aggregate crystals. Some minerals form in geometric shapes, tempered by outside pressures.o Ex. Pyrite has two common crystal shapes (image on pg. 43)- Cleavage: occurs along planes of weakness in relation to atomic bonds. In other words, a mineral may be likely to break apart in areas where its bonds are relatively weak.o Cleavage can occur in one or more directions, which determines its categorization as well as the angles at which the cleavage occurs.o Ex. Mica has sheet (planar) cleavage: the mineral cleaves in only one direction. Mica is known for its perfect cleavage, related to the ease with which the mineral can be cleaved.o Minerals that don’t have cleavage because the bonds are equally strong throughout tend to exude fracture.o Fracture is defined by the way in which a mineral breaks apart when sufficient force is applied. Fracture can be irregular, conchoidal, splintery, fibrous etc.- Hardness: This quality is determined by the propensity and the extent to which a mineral can scratch or be scratched.o Hardness is measured on the Mohs Scaleo The MohsScale consists of 10 minerals arranged by their hardness (10 being the hardest). The minerals are juxtaposed to various devices with which they can be scratched, respectively. o The MohsScale is relative and the numbers are representative of each minerals in a relative and not a compounding sense. (Diagram on pg. 44)- Special properties:Minerals’ properties that go beyond visual cueso Tasteo Smello Feelo Tenacityo reaction to acido magnetismo refractionVII. Natural Resources:- Resources