Classification of Minerals - Hacettepeyunus.hacettepe.edu.tr/~kdirik/JEO_116_2.pdfor more metals. Oxide minerals are the most important ores of iron, manganese, tin, chromium, uranium,

Prof.Dr.Kadir Dirik Lecture Notes

Classification of Minerals

NATIVE ELEMENTSAbout 20 elements occur naturally in their native states as minerals. Fewerthan ten, however, are common enough to be of economic importance. Gold,silver, platinum, and copper are all mined in their pure forms. Iron is rarelyfound in its native state in the Earth’s crust, but metallic iron is common incertain types of meteorites. Native iron and nickel are thought to comprisemost of the Earth’s core.


OXIDESThe oxides are a large group of minerals in which oxygen is combined with oneor more metals. Oxide minerals are the most important ores of iron,manganese, tin, chromium, uranium, titanium, and several other industrialmetals. Hematite (iron oxide, Fe2O3) occurs widely in many types of rocks and isthe most abundant ore of iron. Although typically red in color, it occasionallyoccurs as black crystals used as semiprecious gems. Magnetite (Fe3O4), anaturally magnetic iron oxide, is another ore of iron. Spinel (MgAl2O4) oftenoccurs as attractive red or blue crystals that are used as inexpensive,semiprecious gems. Synthetic spinels are also commonly used in jewelry. Ice,the oxide of hydrogen (H2O), is a common mineral at the Earth’s surface.

SULFIDESSulfide minerals consist of sulfur combined with one or more metals. Manysulfides are extremely important ore minerals. They are the world’s majorsources of copper, lead, zinc, molybdenum, silver, cobalt, mercury, nickel, andseveral other metals. The most common sulfides are pyrite (FeS2), chalcopyrite(CuFeS2), galena (PbS), and sphalerite (ZnS).


SULFATESThe sulfate minerals contain the sulfate complex anion (SO4)2. Gypsum (CaSO42H2O) and anhydrite (CaSO4) are two important industrial sulfates used tomanufacture plaster and sheetrock. Both form by evaporation of seawater orsalty lake water.PHOSPHATESPhosphate minerals contain the complex anion (PO4)3. Apatite,Ca5(F,Cl,OH)(PO4)3, is the substance that makes up both teeth and bones.Phosphate is an essential fertilizer in modern agriculture. It is mined from fossilbone beds near Tampa, Florida, and from great sedimentary apatite deposits inthe northern Rocky Mountains.CARBONATESThe complex carbonate anion (CO3)2 is the basis of two common rock‐formingminerals, calcite (CaCO3) and dolomite [CaMg(CO3)2] . Most limestone iscomposed of calcite, and dolomite makes up the similar rock that is also calleddolomite or sometimes dolostone. Limestone is mined as a raw ingredient ofcement. Aragonite is a polymorph of calcite that makes up the shells of manymarine animals.

SILICATESThe silicate minerals contain the (SiO4)4 complex anion. Silicates make up about 95 percent of the Earth’s crust. They are so abundant for two reasons. First, silicon and oxygen are the two most plentiful elements in the crust. Second, silicon and oxygen combine readily.To understand the silicate minerals, remember four principles:1. Every silicon atom surrounds itself with four oxygens. The bonds between each silicon and its four oxygens are very strong.2. The silicon atom and its four oxygens form a pyramid‐shaped structure called the silicate tetrahedron with silicon in the center and oxygens at thefour corners. The silicate tetrahedron has a 4 charge and forms the (SiO4)4 complex anion. The silicate tetrahedron is the fundamental building block of all silicate minerals.3. To make silicate minerals electrically neutral, other cations must combine with the silicate tetrahedra to balance their negative charges. (The lone exceptionis quartz, in which the positive charges on the silicons exactly balance the negative ones on the oxygens.4. Silicate tetrahedra commonly link together by sharing oxygens. Thus, two tetrahedra may share a single oxygen, bonding the tetrahedra together.


The silicate tetrahedron consists of one silicon atom surrounded by four oxygens. It is the fundamental building block of all silicate minerals.


Rock-Forming Silicate MineralsThe rock‐forming silicates (and most other silicate minerals) fall into five classes,based on five ways in which tetrahedra share oxygens. Each class contains atleast one of the rock‐forming mineral groups.1. In independent tetrahedra silicates, adjacent tetrahedra do not shareoxygens. Rocks composed mostly of olivine and pyroxene made up most of the mantle.2. In the single‐chain silicates, each tetrahedron links to two others by sharingoxygens, forming a continuous chain of tetrahedra. The pyroxenes are a group ofsimilar minerals with single chain structures. Pyroxenes are a major componentof both oceanic crust and the mantle and are also abundant in some continentalrocks.


3. Double‐chain silicates consist of two single chains crosslinked by the sharing ofadditional oxygens between them. The amphiboles are a group of double‐chainsilicates with similar properties. They occur commonly in many continental rocks.4. In the sheet silicates, each tetrahedron shares oxygens with three others in thesame plane, forming a continuous sheet. All of the atoms within each sheet arestrongly bonded, but each sheet is only weakly bonded to those above and below.Therefore, sheet silicates have excellent cleavage. The micas are sheet silicatesand typically grow as plate‐shaped crystals, with flat surfaces. Mica is common incontinental rocks.


The clay minerals are similar to mica in structure, composition, and platy habit.Individual clay crystals are so small that they can barely be seen with a goodoptical microscope. Most clay forms when other minerals weather at the Earth’ssurface. Thus, clay minerals are abundant near the Earth’s surface and are animportant component of soil and of sedimentary rocks.5. In the framework silicates, each tetrahedron shares all four of its oxygenswith adjacent tetrahedra. Because tetrahedra share oxygens in all directions,minerals with the framework structure tend to grow blocky crystals that havesimilar dimensions in all directions. Feldspar and quartz have frameworkstructures.


ROCK-FORMING MINERALS, ACCESSORY MINERALS, GEMS, ORE MINERALS, AND INDUSTRIAL MINERALS

Although about 3500 minerals are known to exist in the Earth’s crust, only a small number—between 50 and 100—are important because they are common or valuable.

ROCK‐FORMING MINERALSThe rock‐forming minerals make up the bulk of most rocks in the Earth’scrust. They are important to geologists simply because they are the mostcommon minerals. They are olivine, pyroxene, amphibole, mica, the clayminerals, feldspar, quartz, calcite, and dolomite. The first six minerals in thislist are actually mineral “groups,” in which each group contains severalvarieties Rock‐Forming Minerals, Accessory Minerals, Gems, Ore Minerals,and Industrial Minerals with very similar chemical compositions, crystallinestructures, and appearances.


ACCESSORY MINERALSAccessory minerals are minerals that are common but usually are found only insmall amounts. Chlorite, garnet, hematite, limonite, magnetite, and pyrite arecommon accessory minerals

ORE MINERALSOre minerals are minerals from which metals or other elements can beprofitably recovered. A few, such as native gold and native silver, are composedof a single element. However, most metals are chemically bonded to anions.Copper, lead, and zinc are commonly bonded to sulfur to form the importantore minerals chalcopyrite, galena, and sphalerite.

GEMSA gem is a mineral that is prized primarily for its beauty, although some gems, likediamonds, are also used industrially. Depending on its value, a gem can be eitherprecious or semiprecious. Precious gems include diamond, emerald, ruby, andsapphire. Several varieties of quartz, including amethyst, agate, jasper, and tiger’seye, are semiprecious gems. Garnet, olivine, topaz, turquoise, and many otherminerals sometimes occur as aesthetically pleasing semiprecious gems


INDUSTRIAL MINERALSSeveral minerals are industrially important, although they are not consideredore because they are mined for purposes other than the extraction of metals.Halite is mined for table salt, and gypsum is mined as the raw material forplaster and sheetrock. Apatite and other phosphorus minerals are sources ofthe phosphate fertilizers crucial to modern agriculture. Many limestones aremade up of nearly pure calcite and are mined as the raw material of cement.


Minerals are the building blocks of rocks

Rocks are defied as as a solid aggregate of one or more minerals.


There are three major groups of rocks namely, igneous, sedimentary and metamorphic.


The three rock groups are formed in different environments by different geologicprocesses.


Igneous rocks


Sedimentary rocks


Metamorphic rocks


Weathering

Transportation

Deposition

Sediments

Igneous rocks(ıntrusion)

Pyroclasticmaterial

Sedimantaryrocks

Metamorphicrocks

Igneous rocks(extrusive)

Uplift & exposure

Crystallization

Melting

Lithification(Compaction andCementation)

Consolidation

All the tree basic group of rocks can evolve from one to another. This concept is named as a rock cycle showing the interrelationships between Earth’s internaland external processes and how three types of groups are related.


Documents

Classification of Minerals - Hacettepeyunus.hacettepe.edu.tr/~kdirik/JEO_116_2.pdfor more metals. Oxide minerals are the most important ores of iron, manganese, tin, chromium, uranium,