MINERALOGY GROUP 2 Arcilla, Laurence Cacatian, Jesley Carlos, Aristotle Celestion, Karl Daniel Colorico, Carlo Mendoza, Arnold Joseph Symmetry Elements of Crystallographic Systems A mineral specimen can be an object of beauty in those occasional circumstances where it forms a single crystal or cluster of crystals. The requirements are that the mineral has been free to grow outwards into the solution or melt from which it formed, not obstructed by other solid matter, nor hindered anywhere around it by a shortage of the constituents needed for growth. In such an environment, it develops a regular pattern of faces and angles between the faces, which is characteristic of a particular mineral. The study of this regularity of form, and of the internal structure of the mineral to which it is related, is called crystallography. In most mineral specimens, the local conditions have hindered or prevented some of the faces from developing, or the surface of the mineral is formed simply from the fractures along which it was broken off when collected. Even in these specimens, there is the same regular internal arrangement of atoms as in a perfect crystal of the same mineral. The specimen is crystalline even though it is not a crystal. Furthermore, in an imperfect crystal, where some faces have developed more than others to produce a distorted external form, the angles between the faces are still the same as in a perfect crystal. A study of the regularity of crystal forms, including the values of interfacial angles, shows that all crystals possess certain elements of symmetry. These elements include: (a) a centre of symmetry, which a crystal possesses when all its faces occur in parallel pairs on opposite sides of the crystal. A cube, for example, possesses a centre of symmetry but a tetrahedron does not. If an imaginary straight line can be passed through a crystal from any point on the surface of crystal such that the point of entry is similar to the point of exit, then the crystal has a center of symmetry. (b) an axis of symmetry, which is a line through a crystal such that a complete rotation of 360° about it produces more than one identical view. There are four types of axis of symmetry: a diad axis, when the same view is seen twice (every 180°); a triad axis, when the same view is seen three times (every 120°); a tetrad axis (four times—every 90°), and finally a hexad axis (six times—every 60°). When an imaginary line can be passed through a crystal such that the crystal can be rotated 360o about the line to fill the same space two, three, four, or six times, it has an axis of symmetry. (c) a plane of symmetry, which divides the crystal into halves, each of which is a mirror image of the other without rotation. When an imaginary plane is passed through a crystal such that the portion of the crystal on one side of the plane is a reflection, or mirror image, of the portion on the other side of the plane, the plane is a plane of symmetry (often called a mirror plane). Physical Properties of Mineral Minerals can be identified by their physical properties that are usually used by mineralogists to help identify a specimen. The list of properties is in a suggested order, progressing from simple experimentation and observation to more complicated, either in procedure or concept. 1. Color -This is typically the first property and most basic way of identifying a mineral, however, it may also be the most difficult property to identify. Especially in translucent to transparent minerals as it has a much more varied degree of color. -Color is often unreliable diagnostic property for two reasons: >Most minerals are colorless or they have same color. >Impurities and trace minerals can alter the actual color of the mineral. 2. Streak -Also called “powder color” of a mineral. -It refers to the colored residue left by the scratch of a mineral on an abrasive surface. -Useful to distinguish two minerals that have the same color, but a different streak -More reliable property of minerals than color for identification. -e.g. Distinguishing Gold from Pyrite, Gold has yellow streak, Pyrite has a greenish black streak 3. Hardness - It is the measure of the mineral’s resistance to scratching. - For example, if mineral A scratches mineral B, and mineral B does not scratch mineral A, then mineral A is harder than mineral B. If mineral A and B both scratch each other, then their hardness is equal. -A scale to measure hardness was invented by German geologist and mineralogist named Frederick Mohs (1822). 4. Crystalline Structure -The particular shape is determined by the arrangement of the atoms, molecules or ions that make up the crystal and how they are joined. -Crystalline structure is one of the two types of structural ordering of atoms, and the other one is amorphous structure. Crystalline structure – Particles are arranged in a repeating pattern. They have a regular and ordered arrangement resulting in a definite shape. Amorphous structure –comes from the Greek ámorphos, meaning “shapeless”. Particles are arranged randomly. They do not have an ordered arrangement resulting in irregular shapes. 5. Cleavage and Fracture -Cleavage and fracture are used to describe how minerals break into pieces. Cleavage is the tendency of a crystal to break along smooth, flat planes of structural weakness Fracture is the tendency of a mineral o break along the curved surface with irregular shapes. The minerals that undergo fracture do not have planes of weakness, therefore break in an irregular manner. 6. Diaphaneity or Transparency -Diaphaneity is a mineral’s degree of transparency or ability to allow light to pass through it. The degree of transparency may also depend on the thickness of the mineral. 7. Tenacity -Describes the reaction of mineral to stress such as crushing, bending, breaking or tearing. Certain minerals react differently to each type of stress. Since tenacity is composed of several reactions to various stresses, it is possible for a mineral to have more than one type of tenacity. The different types of tenacity are: I. Brittle -Mineral crumbles to grains or powder when hammered. -e.g., quartz, calcite, fluorite II. Sectile -Sectile minerals can be separated with a knife, much like wax but usually not as soft. -e.g., Talc, Graphite III. Malleable -If a mineral can be flattened by pounding with a hammer, it is malleable. All true metals are malleable. -e.g., silver, gold IV. Ductile -A mineral that can be stretched into a wire is ductile. All true minerals are ductile. -e.g., gold V. Flexible but inelastic -Any mineral that can be bent, but remains in the new position after it is bent. -e.g., copper VI. Flexible and elastic -When flexible and elastic minerals are bent, they spring back to their original position. -e.g., biotite 8. Magnetism -Several minerals react when placed within a magnetic field. Some minerals are attracted to the magnet, others are weakly attracted, and one mineral is repelled. There are also several minerals that are attracted to magnetic fields only when heated. -The presence of iron in a mineral is responsible for the magnetic properties of minerals in virtually all cases. -To test a mineral for magnetism, just put the magnet and mineral together and see if they are attracted. -Magnetite is the only common mineral that is always strongly magnetic. 9. Luster -Shows how much light is reflected in a mineral and how brilliant or dull the mineral is. -Often described as either metallic or non-metallic. I. Metallic luster -Is for minerals that are opaque and reflective and have the look of polished metal. - Some common examples are different pyrites, which are used to make coins, gold nuggets, and copper. >Submetallic luster- is one that resembles a metal but, due to weathering and corrosion, have become less reflective or dull. Some examples are sphalerite and cinnabar. II. Non-metallic luster -Minerals may be shiny and reflect light, however, they do not look like a metal. Types of Non-metallic luster: Adamantine -Minerals that have remarkable shine and brilliance and have the hard look of a diamond. These minerals can be transparent or translucent, and the most popular examples are found in jewelry and accessory stores: diamonds and cubic zirconia. Dull -Dull luster is also known as 'earthy' and is used to describe minerals that have poor reflectivity. The surface of minerals with dull luster is coarse and porous. Some examples are kaolinite and montmorillonite. Vitreous -The reflective property of minerals with vitreous luster is similar to that of glass. This is a very common type of luster and can occur in minerals that are transparent or translucent. Some of these minerals are quartz and calcite. Greasy -The greasy type of luster can be found in minerals that look like they were coated with oil or grease. These minerals can also be said to resemble fat, and they also feel greasy to touch. Some examples are opal and halite. 10. Odor and Taste -Some minerals have a distinctive taste and some have distinctive odor. -Only soluble minerals have a taste, but it is very important that minerals not be placed in the mouth or on the tongue. You should not test for this property in the classroom. -Most minerals have no odor unless they are acted upon in one of the following ways: moistened, heated, breathed upon, or rubbed. 11. Specific Gravity -The specific gravity of a mineral is the ratio of its weight compared to the weight of an equal volume of water. -Substance that have specific gravity less than 1 are lighter than water, greater than 1 are heavier than water. Study of the Rock Forming Minerals Quartz Family -One of the most well-known minerals on Earth. -It is a mineral composed of silicon dioxide (SiO2) -They are developing in various shades, ranging from transparent clarity to opaque, solid colors -It occurs in igneous, metamorphic and clastic rocks, especially in granite and other felsic formation. -Quartz Color: colorless, white, purple, pink, brown, and black. Also, gray, green, orange, yellow, blue and red. Sometimes multicolored or bald. -Quartz Specific Gravity or Density: 2.6 to 2.7 -Quartz hardness rating: Mohs Scale of 7 -Quartz Crystal System: Trigonal or Rhombohedral each crystal cell has “six faces, of which have two pairs of parallel sides. -Quartz Refractive Index: ranges from 1.543 to 1.553 -It has many uses, glass, optics, sand for construction and building, part of cement and plaster. -It also used as building stone, pottery and flux in metallurgical applications. -Large amount of quartz sand are used in the manufacture of glass and ceramics and for foundry molds in metal casting. Feldspar Family -It is the single most abundant mineral group on Earth. -Grouped of minerals distinguished by the presence of alumina and silica (SiO2) -They are mined from large granite bodies (called plutons by the geologists), from pegmatite’s (formed when the last fluid stages of a crystallizing granite become concentrated in small liquid vapor rich pockets that allow the growth of extremely large crystals) and from sand composed mostly of feldspar. -Feldspar Color: white, pink, gray or brown. Also, colorless, yellow, orange, red, black, blue, green -Feldspar Specific Gravity or Density: 2.5 to 2.8 -Feldspar Hardness rating: Mohs Scale of 6 t 6.5 -Feldspar Crystal System: Triclinic, monoclinic -It is used widely in the glass and ceramics industries -Is used to make dinnerware and bathroom and building tiles -In ceramic and glass production, it is used as a flux Augite -It is an important rock forming mineral, and large crystals are fairly common -It is the most common pyroxene mineral and a member of the clinopyroxene group -It is also found in ultrafamic rocks and in some metamorphic rocks that form under high temperatures -They occur in dull crystals that are ugly and uninteresting. -Augite color: Dark green, black, brown -Augite Specific Gravity or Density: 3.2 to 3.6 -Augite Hardness rating: Mohs Scale of 5.5 to 6 -Augite Crystal System: Monoclinic -It may be found in certain metamorphic rocks, notably marbles. Hornblende -Rock forming element that is an important constituent in acidic and intermediate igneous rocks -It is an inosilicate amphibole mineral -Hornblende Color: Black, dark green, dark brown -Hornblende Specific Gravity or Density: 2.9 to 3.5 (varies depending upon composition) -Hornblende Hardness rating: Mohs Scale of 5 to 6 -Hornblende Crystal System: Monoclinic -It is used for highway construction and as a railroad ballast -Is use as building facing, floor tiles, countertops, and other architectural uses -Has been used to estimate the depth of crystallization of plutonic rocks Biotite -Is a very common and widespread mineral group -Occur in metamorphic and igneous rocks -It is one of the two most common members of mica group -Their structures are composed of many sheet-like layers which are connected to each-other by weak chemical bonds. -Biotite Color: Black, dark green, dark brown -Biotite Specific Gravity or Density: 2.7 to 3.4 -Biotite Hardness rating: Mohs Scale 2.5 to 3 -Biotite Crystal System: Monoclinic -It is used extensively to constrain ages of rocks, by either potassium-argon dating or argonargon dating -Is used as a filter and extender in paints, as an additive to drilling muds, as an inert filter and mold release agent in rubber, products, and as a non-stick surface coating on asphalt shingles and rolled roofing Muscovite -It is an important rock forming mineral present in igneous, metamorphic, and sedimentary rocks. -Muscovite sheets have a pearly to vitreous luster on their surface. -Muscovite Color: Thick specimens often appear to be black, brown, or silver in color; however, when split into thin sheets it is colorless, sometimes with a tint of brown, yellow, green, or rose -Muscovite Specific Gravity or Density: 2.8 to 2.9 -Muscovite Hardness rating: Mohs Scale 2.5 to 3 -Muscovite Crystal System: Monoclinic -It is use in joint compound used to finish seams and blemishes in gypsum wallboard -It serves as a filler, improves the workability of the compound, and reduces cracking in the finished product -Is an additive to drilling mud that helps to seal porous sections of the drill hole to reduce circulation loss. Calcite -It is a rock forming mineral with a chemical formula of CaCO3 -It is extremely common and found throughout the world in sedimentary, metamorphic and igneous rocks. -Some geologists consider it to be “ubiquitous mineral” -It is the principal constituent of limestone and marble and serve as one of the largest carbon repositories on our planet -Calcite Color: Usually white but also colorless, gray, red, green, blue, yellow, brown, orange Calcite Specific Gravity or Density: 2.7 -Calcite Hardness rating: Mohs Scale of 3 Calcite Crystal System: Hexagonal -It is used as a construction material, abrasive, agricultural soil treatment, construction aggregate, pigment, pharmaceutical and more Garnet -Member of a group of common silicate minerals that have similar crystal structures and chemical compositions -The rock forming garnets are most common in metamorphic rocks -Few occur in igneous rocks, especially granites and granitic pegmatites. -Garnet Color: Typically, red, but can be orange, green, yellow, purple, black or brown (Blue garnets are extremely rare) -Garnet Specific Gravity or Density: 3.5 to 4.3 -Garnet Hardness rating: Mohs Scale 6.5 to 7.5 -Garnet Crystal System: Isometric -It is used in waterjet cutting, “sand” blasting, sandpaper, water filtration, and a number of other uses. -Garnets are used in waterjet cutting machines for the cutting of concrete, aluminum, high strength steel, marble, granite, automotive glass, plastic laminates, titanium, aerospace composites, steel bridge decking, and textile, among others -Garnet grains can be used as a filtration media in water treatment facilities. Its high specific gravity, as well as, chemical and abrasive resistance makes it an ideal filter media for water purification purposes -In industries, they are used to produce sandpapers. Process of Formation of All Minerals Minerals can develop under wide variety of geological conditions. There are potentially more ways to make minerals than there are various types of minerals. Minerals may form as a result of: •Volcanic gases •Sediment formation •Oxidation •Magma crystallization or saline fluid deposition. Here are some methods of Mineral Formation: Formation from Hot Material A rock is a collection of minerals. Imagine a rock that becomes so hot it melts. Many minerals start out in liquids that are hot enough to melt rocks. Magma is melted rock inside Earth, a molten mixture of substances that can be hotter than 1,000oC. Magma cools slowly inside Earth, which gives mineral crystals time to grow large enough to be seen clearly. Formation from Solutions Water on Earth, such as the water in the oceans, contains chemical elements mixed into a solution. Various processes can cause these elements to combine to form solid mineral deposits. Minerals from Salt Water When water evaporates, it leaves behind a solid precipitate of minerals. Minerals from Hot Underground Water Magma heats nearby underground water, which reacts with the rocks around it to pick up dissolved particles. As the water flows through open spaces in the rock and cools, it deposits solid minerals. The mineral deposits that form when a mineral fills cracks in rocks are called veins. Physical and chemical conditions include factors such as temperature, pressure, presence of water, pH, and amount of oxygen available. Time is one of the most important factors because it takes time for atoms to become ordered. If time is limited, the mineral grains will remain very small. The presence of water enhances the mobility of ions and can lead to the formation of larger crystals over shorter time periods. Most of the minerals that make up the rocks around us formed through the cooling of molten rock, known as magma. At the high temperatures that exist deep within Earth, some geological materials are liquid. As magma rises up through the crust, either by volcanic eruption or by more gradual processes, it cools and minerals crystallize. •If the cooling process is rapid (minutes, hours, days, or years), the components of the minerals will not have time to become ordered and only small crystals can form before the rock becomes solid. The resulting rock will be fine-grained (i.e., crystals less than 1 mm). •If the cooling is slow (from decades to millions of years), the degree of ordering will be higher and relatively large crystals will form. In some cases, the cooling will be so fast (seconds) that the texture will be glassy, which means that no crystals at all form. There are 4 main categories of Mineral Formation: •Igneous or Magmatic -Igneous rock is formed through the cooling and solidification of magma or lava. There are two subtypes of Igneous Rock: This can happen beneath or above the surface. 1) Intrusive rocks or Plutonic rocks When magma never reaches the surface and cools to form intrusions (dykes, sills etc.) the resulting rocks are called plutonic. Depending on their silica content, they are called (in ascending order of silica content) gabbro, diorite, granite and pegmatite. By quantity, these are the by far most common rock types. Most magmas actually never reach the surface of the earth. 2) Extrusive rocks or Volcanic rocks When magma does reach the surface during a volcanic eruption, the rocks that form there are called lavas or volcanic rocks. The basic classification is the same as for plutonic rocks: with increasing silica content, they include: basalt, andesites, dacites, rhyolite, pumice and obsidian. • Sedimentary -Sedimentary rocks are formed when sediment is deposited out of air, ice, wind, gravity, or water flows carrying the particles in suspension. This sediment is often formed when weathering and erosion break down a rock into loose material in a source area. •Metamorphic -Metamorphic rocks are formed from other rocks that are changed because of heat or pressure. They are not made from molten rock – rocks that do melt form igneous rocks instead. Earth movements can cause rocks to be deeply buried or squeezed. As a result, the rocks are heated and put under great pressure. There are three types of Metamorphism: Contact Metamorphism occurs when magma comes in contact with an already existing body of rock. When this happens the existing rocks, temperature rises and also becomes infiltrated with fluid from the magma. The area affected by the contact of magma is usually small, from 1 to 10 kilometers. Contact metamorphism produces non-foliated (rocks without any cleavage) rocks such as marble, quartzite, and hornfels. Regional Metamorphism occurs over a much larger area. This metamorphism produces rocks such as gneiss and schist. Regional metamorphism is caused by large geologic processes such as mountain-building. These rocks when exposed to the surface show the unbelievable pressure that cause the rocks to be bent and broken by the mountain building process. Regional metamorphism usually produces foliated rocks such as gneiss and schist. Dynamic Metamorphism also occurs because of mountain-building. These huge forces of heat and pressure cause the rocks to be bent, folded, crushed, flattened, and sheared. •Hydrothermal -Hydrothermal essentially means “hot water.” Hydrothermal rocks are those rocks whose minerals crystallized from hot water or whose minerals have been altered by hot water passing through them. Thus, these rocks are distinct from metamorphic rocks, which are created by solid‐state mineral transformations. Coal and Petroleum - Their history and occurrence in India Millions of years ago, algae and plants lived in shallow seas. After dying and sinking to the seafloor, the organic material mixed with other sediments and was buried. Over millions of years under high pressure and high temperature, the remains of these organisms transformed into what we know today as fossil fuels. Coal, natural gas, and petroleum are all fossil fuels that formed under similar conditions. Coal -Coal is a hard rock which can be burned as a solid fossil fuel. -It is mostly made up of carbon but also contains hydrogen, Sulphur, oxygen and nitrogen. Different Types of Coal There are four types of coal - lignite, sub-bituminous, bituminous and anthracite. Each type has different proportions of carbon and thus, have different uses. Lignite - This type of coal has 40% - 55% carbon content, which implies that moisture content is lesser than the peat variant. This is mainly used in households for cooking and ironing and power plants. Bituminous - The carbon content here is 40% to 80%, which means there is very little moisture. It is used in power plants for creating electricity and is also used for producing steel. Anthracite - With 80% to 90% carbon content, this type has the maximum carbon content with very little moisture. It is used for heating commercial buildings and is the highest variety of coal. Coal is one of the most useful fossil fuels. It can also be processed industrially in order to obtain products like coke, tar and coal gas. These by-products are beneficial to us too. Coke: Coke is a high-carbon product obtained by the destructive distillation of coal. The amount of carbon content in coke is so high that it is said to be an almost pure form of carbon. Uses: -The most common use of coke is as a fuel for stoves, furnaces and blacksmithing. -It is also used to produce iron in a blast furnace. Coal tar: It is obtained as a by-product in the process of making coke. Though its color is the same as coke, tar is a highly viscous liquid. Uses: -Coal tar is widely used to manufacture paints, perfumes, synthetic dyes, photographic material, drugs and explosives. -Coal tar is an ingredient of anti-dandruff and lice-repelling shampoos, soaps and ointments. Coal gas: It is a highly flammable gas as the main component of it is methane. Thus, if not regulated carefully, it can form mixture with air resulting in explosions. Uses: -Earlier, it was used as a source of light. In the year 1820, it was used in London for the first time as street lighting. How Is Coal Obtained? -Coal is extracted by different kinds of mining activities on the Earth’s surface. The most common ones are surface mining and underground mining. Surface mining is done when coal is less than 200 feet below ground level. -Underground mining is performed when the coal is deeper than 300ft below ground level. Coal mine workers have to carry out mining activities then. Types of coal in India Anthracite: It is the highest grade of coal containing a high percentage of fixed carbon. It is hard, brittle, black and lustrous. It is found in smaller quantity in regions of Jammu and Kashmir. Bituminous: It is a medium grade of coal having high heating capacity. It is the most commonly used type of coal for electricity generation in India. Most of bituminous coal is found in Jharkhand, Odisha, West Bengal, Chhattisgarh, and Madhya Pradesh. Subbituminous: It is black in color, dull (not shiny) and has a higher heating value than lignite. Lignite: It is the lowest grade coal with the least carbon content. It is found in the regions of Rajasthan, Tamil Nadu, and Jammu & Kashmir. Petroleum -Petroleum is a substance that occurs naturally. -It is a dark liquid and occurs beneath the earth’s surface. -A large number of products like petrol, diesel, lubricating oil, etc derive from petroleum. Its compounds can be separated with the help of fractional distillation. Petroleum Refining Process An oil refinery or petroleum refinery is an industrial process plant where crude oil is transformed and refined into useful products such as petroleum naphtha, gasoline, diesel fuel, asphalt base, heating oil, kerosene, liquefied petroleum gas, jet fuel and fuel oils. Crude Oil procured from an oil well is a mixture of many liquids. Different temperature evaporates a different liquid. This temperature is the boiling point of that liquid. Products produced in Petroleum Refining Process Petroleum Gas: Generally, liquefied petroleum gas is useful for domestic fuel. Gasoline: Procuration of petrol occurs from this fraction. Kerosene: It is used as domestic fuel and also as fuel in jet engines. Diesel oil or light oil: It is useful in the automobile industry. Heavy Oil or Lubricating Oil: This type of oil is used in making lubricating oils. Fuel Oil: It is essential for ships, central heating, and factories. Residue: We can procure products like paraffin wax, bitumen from this residue. It is useful for making roads and roofing. History and occurrence in India •In 1859, the world’s first oil well was drilled in Pennsylvania, USA. •In 1867, oil was stuck at Makum in Assam, India. •In India, petroleum is largely found in Assam, Gujarat, Mumbai High, Maharashtra, and in the river basins of Godavari and Krishna.
