SH1 63 1 02 Handout 1 *Property of STI student.feedback@sti. edu Page 1 of 11 Mineral and Rock Resources Definition of Terms • Resource - stock or supply of anything that can be drawn on by anyone to function effectively • Mineral - a solid, inorganic substance of natural occurrence • Rock - a conglomerate of various minerals formed on Earth's surface • Ore - naturally - occurring solid where valuable metals and/or minerals extracted for profit Minerals Distinction 1. Naturally Occurring - minerals are made, and exist, naturally 2. Inorganic - minerals aren't made from living organisms 3. Solid - minerals exist in neither liquid nor gas forms 4. Definite chemical composition - minerals are defined by their chemical composition, which must be expressed by their chemical formula in specific ratios 5. Ordered internal structure - minerals must have regular, repetitive geometric patterns or crystal structures Characteristics I. Optical Properties 1. Luster ( l ustre in other references) - property of a mineral to reflect light; describes how brilliant or dull it is Luster Type Description Example Adamantine • Transparent or translucent minerals with very high refractive indices • Gives off brilliance or shine to the minerals Diamond Source: https://geology.com/minerals/photos/dia mond - on - matrix.jpg Earthy / Dull • Exhibits very poor luster • Observed from minerals with rough and/or porous surfaces Kaolinite Source: https://en.wikipedia.org/wiki/Kaolinite Greasy • Has a dull sheen that resembles fat, oil, or it may look like it has been dipped and smoothened in oil • May contain microscopic inclusions • May have a "greasy" feel Nephrite Jade Source: https://www.gia.edu/images/Pic41_187 663 - 468x620.jpg Metallic • Opaque and reflective sheen • Resembles polished metals Pyrite Source: https://tinyrituals.co/blogs/tiny - rituals/pyrite - meaning - healing - properties - everyday - uses Pearly • Resembles a pearl in sheen • Consists of thin coplanar sheets that breaks up light in various layers Muscovite Source: https://en.wikipedia.org/wiki/Muscovite SH1 63 1 02 Handout 1 *Property of STI student.feedback@sti. edu Page 2 of 11 Resinous • Resembles resin, chewing gum, or smooth plastic • Has a "honey - like" sheen, with a "plastic" feel Sulfur Source: https://www.minerals.net/mineral/sulfur. aspx?img=/Image/3/131/Sulfur.aspx Silky • Minerals contain fibrous structures • Resembles silk cloth and/or fiber in terms of optical properties Asbestos Source: https://en.wikipedia.org/wiki/Asbestos Submetallic • Minerals are opaque to semi - opaque • Sheen almost looks similar to metal • Thin splinters of minerals with this luster are translucent Hornblende Source: https://www.minerals.net/mineral/hornbl ende.aspx Vitreous • Almost 65% of minerals have this luster • Minerals have glass - like reflective properties Amethyst (a purple q uartz ) Source: https://en.wikipedia.org/wiki/Amethyst Waxy • Minerals appear to be "coated in wax" • Has a "waxy" feel Turquoise Source: http://legacy.earlham.edu/~norlila/turqu oise.htm 2. Penetrability - optica l property of minerals to allow light to pass through Type Description Transparent • Allows light to pass through • Can sometimes refract light to reveal different wavelengths • Quartz and diamond are some examples Translucent • Allows some light to pass through • Reflects some wavelengths to show color • Most adamantine, vitreous, and resinous minerals with impurities are translucent Opaque • Does not allow light to pass through • Wavelengths not reflected are absorbed instead • Minerals that are not adamantine, resinous, nor vitreous fall into this category 3. Color - an optical perception described through certain color categories (such as red , blue , etc.); considered to be unreliable due to impurities affecting color quality 4. Streak - a mineral's color in powdered form, achieved by rubbing the mineral across an un - wea thered surface, such as an unglazed porcelain; however, minerals with higher hardness cannot leave streak marks on the porcelain SH1 63 1 02 Handout 1 *Property of STI student.feedback@sti. edu Page 3 of 11 II. Mineral Strength 1. Mineral Strength determines how easy minerals break or deform when exposed to stress 2. Tenacity ( or toughness ) refers to the mineral's resistance to breaking or deforming 3. Hardness (or s trength ) is the measure of a mineral's resistance to abrasions (or scratches); see Page 1 of 02 Handout 2 for the Mohs Scale 4. Cleavage is the tendency of minerals to break along the planes of weakness; observed as the splitting between two (2) atomic planes result ing from weaker bond strengths or greater lattice spacing across the plane in question KINDS OF MINERAL CLEAVAGE HABIT Type Description Eminent Mineral cleaves readily and very easily Perfect Mineral surface is smooth and mirror - like Distinct Mineral surface is smooth with minor inconsistencies (e.g., visible cracks, rough edges and/or exterior) Difficult Mineral surface contains inconsistencies after cleavage, may tend to fracture than to cleave Indistinct Mineral surface is present but is barely noticeable None No cleavage available CLEAVAGE HABITS HABIT Type Description and Cleavage Direction Basal / Pinacoidal Cleaves at the base, one (1) direction Cubic Cleaves as cubes, three (3) directions at right angles Dodecahedral Cleaves as dodecahedrons, six (6) directions Octahedral Cleaves as octahedrons, four (4) directions Prismatic Cleaves to form prisms, two (2) directions Rhombohedral Cleaves into rhombohedrons, three (3) directions not at right angles 5. Fracture is a form of splitting where a mineral is split despite not having any cleavage plane due to its strong chemical bonds between the mineral's atoms FRACTURE HABITS HABIT Type Description Conchoidal • Sometimes referred to as a shelly • Fracture resembles a semicircular shell with a smooth, curved surface • Can be seen in broken glass Uneven • Fracture leaves a rough or irregular surface Hackly • aka. Jagged fracture • Fracture resembles a broken metal • Fracture has rough, jagged points • Seen in true metals Splintery • Fracture forms elongated splinters • Exhibited by fibrous minerals Earthy • aka. Crumbly fracture • Mineral crumbles upon fracture, reminiscent of dry earth Smooth • aka. Even fractures • Fracture with a smooth surface reminiscent of a perfect cleavage Subconchoidal • Cross between a conchoidal and smooth fractures • Fracture with a smooth, yet irregular rounded corners III. Specific Gravity Specific Gravity is the measure of a mineral's density. It is the weight of a mineral relative to the weight of an equal volume of water. Since water has a specific gravity of one (1), any material whose specific gravity is greater than one (1) is denser than water. Likewise, materials with specific gravities lower than one (1) are less thick. SH1 63 1 02 Handout 1 *Property of STI student.feedback@sti. edu Page 4 of 11 Common Rock - Forming Minerals Quartz Silica Source: https://en.wikipedia.org/wiki/Quartz Chemical Composition 𝐒𝐢𝐎 𝟐 Luster Vitreous Transparency Transparent (can also be translucent) Color Mostly clear. It can also be: • Purple (Amethyst) • Yellow to Brown (Citrine) • Grey (Smoky Quartz) • Pink (Rose Quartz) • White (Milky Quartz) • Green (Prasiolite) Streak White Crystal Shape Prismatic Hardness 7 .0 Cleavage / Fracture Fracture ( C onchoidal) Specific Gravity ( g / cm 3 ) 2.65 Feldspar Orthoclase Source: https://en.wikipedia.org/wiki/Orthoclase Plagioclase Source: https://en.wikipedia.org/wiki/Plagioclase Chemical Composition Orthoclase 𝐊𝐀𝐥𝐒𝐢 𝟑 𝐎 𝟖 Plagioclase 𝐂𝐚𝐀𝐥 𝟐 𝐒 𝐢 𝟐 𝐎 𝟖 , 𝐍𝐚𝐀𝐥𝐒 𝐢 𝟑 𝐎 𝟖 Luster Vitreous Transparency Opaque Color Orthoclase • Red • Pink • White Plagioclase • Green • Grey • White Streak Orthoclase White Plagioclase -- n/a -- Crystal Shape Prismatic or Tabular Hardness Orthoclase 6 Plagioclase 6.0 - 6.5 Cleavage / Fracture Cleavage (Perfect, P rismatic) Specific Gravity ( g / cm 3 ) Orthoclase 2.6 Plagioclase 2.6 - 2.8 SH1 63 1 02 Handout 1 *Property of STI student.feedback@sti. edu Page 5 of 11 Mica Muscovite Source: https://en.wikipedia.org/wiki/Muscovite Biotite Source: https://en.wikipedia.org/wiki/Biotite Chemical Composition Muscovite 𝐊𝐀𝐥 𝟑 𝐒𝐢 𝟑 𝐎 𝟏𝟎 ( 𝐎𝐇 ) 𝟐 Biotite 𝐊 ( 𝐅𝐞 , 𝐌𝐠 ) 𝟑 𝐀𝐥𝐒𝐢 𝟑 𝐎 𝟏𝟎 ( 𝐎𝐇 ) 𝟐 Luster Vitreous to Pearly Transparency Transparent to translucent Color Muscovite • White • Silver • Yellow • Green • Brown Biotite Brown to Black Streak Muscovite White Biotite Very pale brown Crystal Shape Tabular Hardness Muscovite 2.0 - 2.5 Biotite 2.5 - 3.0 Cleavage / Fracture Cleavage (Perfect, Basal) Specific Gravity ( g / cm 3 ) Muscovite 2.8 Biotite 2.9 - 3.4 Pyroxene Augite Source: https://en.wikipedia.org/wiki/Augite Chemical Composition ( 𝐌𝐠 , 𝐅𝐞 ) 𝐒𝐢𝐎 𝟑 Luster Vitreous Transparency Mostly translucent (opaque in others) Color Dark Green to Black Streak Greenish white Crystal Shape Crystals can be: • Prismatic • Tabular • Granular Hardness 5.0 - 6.0 Cleavage / Fracture • Cleavage (Rhombohedral) • Fracture ( U neven) Specific Gravity ( g / cm 3 ) 3.2 - 3.6 Amphibole Hornblende Source: https://en.wikipedia.org/wiki/Hornblende Chemical Composition 𝐂𝐚 𝟐 ( 𝐅𝐞 , 𝐌𝐠 ) 𝟓 𝐒 𝐢 𝟖 𝐎 𝟐𝟐 ( 𝐎𝐇 ) 𝟐 Luster Vitreous Transparency Opaque Color Dark Green to Black Streak Dark g reen SH1 63 1 02 Handout 1 *Property of STI student.feedback@sti. edu Page 6 of 11 Crystal Shape Crystals can be: • Prismatic • Fibrous • Granular Hardness 5.0 - 6.0 Cleavage / Fracture • Cleavage (Imperfect, Prismatic) • Fracture (Uneven) Specific Gravity ( g / cm 3 ) 2.9 - 3.4 Olivine Olivine Source: https://en.wikipedia.org/wiki/Olivine Chemical Composition ( 𝐌𝐠 , 𝐅𝐞 ) 𝟐 𝐒𝐢𝐎 𝟒 Luster Vitreous Transparency Translucent Color Yellow Green Streak White Crystal Shape Granular Hardness 6.5 - 7 Cleavage / Fracture Fracture (Conchoidal) Specific Gravity ( g / cm 3 ) 3.2 - 4.4 Calcite Calcium carbonate Source: https://en.wikipedia.org/wiki/Calcite Chemical Composition 𝐂𝐚𝐂𝐎 𝟑 Luster Vitreous to resinous Transparency Transparent to translucent Color Generally White Streak White Crystal Shape Crystals can be: • Prismatic • Granular Hardness 3.0 Cleavage / Fracture • Cleavage (Perfect, Cubic) • Fracture ( Conchoidal ) Specific Gravity ( g / cm 3 ) 2.7 General Crystal Shapes HABIT Type Description Example Acicular • Crystals have a needle - like shape that ends in a blunt termination. • Can cluster to form fan - shaped or radially - shaped aggregates • Used when an individual crystal's length is greater than its width or diameter Banded • Have narrow layers (bands) of different color and/or texture • May be a response to changes in the composition of the mineral's growth, the sedimentary process, or other conditions SH1 63 1 02 Handout 1 *Property of STI student.feedback@sti. edu Page 7 of 11 Bladed • Elongated crystals whose length exceeds the width and its width exceeds the mineral's thickness • Ends sometimes taper to a point • Shaped similarly to a sword or knife blade Botryoidal • aka. globular or mammillary • Gk. botruoeides , "a bunch of grapes" • Mineral aggregates are round Columnar • Long prisms whose widths exceeds the acicular type • May contain multiple parallel crystals in one "column" Cubic • Crystals with six square faces and four - fold rotational symmetry around three (3) axes Dendritic • Minerals that form a branching pattern similar to a tree or a leaf vein • Gk. d endron , "tree" D odecahedral • Minerals that have 12 flat faces Drusy • Surface is covered in small crystals (druse) Fibrous • Minerals occur in very fine, fiber - like crystals, reminiscent of hair or fur • Thinner than acicular crystals • Aggregates similarly with acicular crystals Foliated • aka. micaceous , as most mica minerals have this habit • Sheet - like crystal habit • Minerals with this habit can be cut into thin sheets SH1 63 1 02 Handout 1 *Property of STI student.feedback@sti. edu Page 8 of 11 Geodic • Minerals aggregate in rounded or oblate masses through crystallization on the inside walls of a hollow cavity • Bands eventually develop, gradually filling in the cavity without filling it completely • These aggregates are called geodes Granular • Aggregations made of many rounded or equant anhedral crystals of similar sizes • Can be loose without any interstitial material, or could be interlocking with other materials Hopper • Partially - formed crystals that have experienced more rapid growth on the outer edges than in the center • Well - developed outer s ides, "hollow" center • Can be considered as an "innie" Massive • Crystals with no distinctive geometry or habit Nodular • Crystals grow to form rounded/ bulbous structures • Usually arranged in radial structures within the nodule • Nodule may experience concentric banding Octahedral • Crystals form into an octahedral shape • Octahedrons have eight (8) triangular faces and three (3) axes of four - fold rotational symmetry Oolitic • Occur in crystalline aggregates that are rounded and less than 4 mm in size • Smaller version of pisolites Pisolitic • Occur in crystalline aggregates that are rounded and about the size of peas • Individual pisolites are made of many tiny radiating mineral crystals Prismatic • Minerals that form in elongated crystals with opposite faces usually parallel to each other • Often striated either along the length or across the width SH1 63 1 02 Handout 1 *Property of STI student.feedback@sti. edu Page 9 of 11 Radiating • Aggregates grow outwards from a central point • Consist of multiple crystals growing in diverging directions Rosette • Cluste rs of tabular crystals in a radial arrangement that have external geometry resembling a rose or a flower Stalactitic • Used for specimens that formed as stalactites or stalagmites • Often grow downwards or upwards in a cavity or a cavern • Still have radial cross - sections Striated • Striations are fine, slightly indented lines present on the faces of some crystals • Striations are always parallel to the crystallographic axis and one (1) edge of the crystal face Tabular • Flat and plate - like • Length and width are larger than the thickness • Known as stone tablets Sources: https://geology.com/minerals/crystal - habit/ Rocks Things to Remember • Rocks are part of the Earth's lithosphere o Lithosphere [Gk. lithos - , "stone" ; sphaira , "ball, sphere" ] is the rigid outer part of the Earth's subsystem, consisting of the crust and upper mantle. • Rocks are ever - changing in its form and composition, as shown in the rock cycle. • There are three kinds of rocks: o Igneous rocks [Lat. Igneus , "fiery" (from ignis , "fire")] are rocks made from the cooling of molten material, such as magma , lava , and other pyroclastics. The subsequent development of igneous rocks create s uplift , which expose s them to weathering and erosion. o Sedimentary rocks are rocks made from cementing and compacting eroded materials from other rocks called sediments [derived Lat. Sedimentum , "settling , sinking down " (from sedeo , "to sit")] ▪ Weathering is the process of breaking down pieces of material, such as rocks, soil , and other materials, through contact with the atmosphere, water, or living organisms. ▪ Erosion is the process where agents of weathering are moving in a single direction and carry away the weathered materials with them. o Metamorphic rocks are rocks made th rough the process of metamorphism [Gk. meta - , "beyond, above, transcending"; morphe , "form, shape"] , where pressure and temperature dictate its new properties. Formation of Igneous Rocks The formation of igneous rocks depend s wholly on how fast the material cools down and where they cooled down. They can be classified into: 1. Formation by slow cooling - Igneous rocks that form in this method require that magma cools slowly to allow the minerals to realign themselves and SH1 63 1 02 Handout 1 *Property of STI student.feedback@sti. edu Page 10 of 11 recrystallize. These rocks (called plutonic rocks ) have large crystal structures visible to the naked eye. Examples : granite, diorite, syenite 2. Formation by rapid cooling - Igneous rocks that form in this method require that free - flowing lava must be cooled quickly, creating rocks that are glass - like in appearance and properties. This is because the minerals aren't given enough time to re crystallize, creating minimal mineral crystals that aren't visible to the naked eye. Examples : basalt, obsidian, andesite, rhyolite 3. Formation as pyroclastics - Igneous rocks that form in this method are created when lava is extruded violently from the volcano. Depending on the amount of trapped gases in the lava, the resulting materials can be as small as ash, or large enough to be called rocks (called pyroclas tic rocks ). Examples : ignimbrite (or adobe ) , tuff, volcanic breccia , scoria, pumice Formation of Sedimentary Rocks 1. Formation by cementation - Sedimentary rocks can form through compaction and cementation of particulates that have been eroded. These sediments are carried off from faraway sources, which are then deposited, buried, and undergo compaction and cementation . Combining both compaction a nd cementation yields lithification , the process that converts sediments into sedimentary rocks However, there are two things to consider: a. If the materials are purely mineral in origin , including other large debris caught in the compaction , they are called clastic rocks Examples : sandstone, shale, conglomerate b. If the materials contain any biological remains, such as shells, bones, or trapped resins among others , they are called bioclastic rocks Examples : coquina, organic limestone 2. Formation by chemical precipitation - Sediments can also come in the form of saturated liquids that have precipitated down from the solution made during the erosion process. Once the sediments precipitate downward, and if there are minimal foreign inclusions and/or contaminations, they can form rocks made of similar materia ls, which can be called chemical rocks , because these are made from precipitated ions of other rocks Examples : halite (salt), limestone, dolostone Formation of Metamorphic Rocks When metamorphic rocks are formed, two things govern their formation: temperature and pressure. The pressure adds considerable stress on the rocks. This , in turn, increases heat in the material. The temperature must be hot enough to incur changes in the rock, but not hot to melt the rock during metamorphism. However, the instances of metamorphism can be dictated by which the agent acts more on the process. 1. Formatio n through pressure - metamorphic rocks formed primarily by pressure reveals the banded "layers" of the various materials of the original rock Heat and pressure slowly press upon these materials, which can be observed in moving tectonic plates. These band s form perpendicularly from the direction of the pressure. The final product is then called a foliated or regional rock due to the bands being called foliation [Lat. Folium , "a leaf"] formed in tectonic regions Examples : gneiss (pronounced as nice , made from shale or granite), schist (made from shale turning to slate, then to phyllite), slate (made from shale) 2. Formation through temperature - This process of metamorphism is best observed when the subject rock is exposed to older rock and an intruding body of magma Under these conditions, it may either undergo recrystallization or fundamentally change its mineralogy (if there are chemically - act ive fluids present). This process is called contact metamorphism , as the rocks this creates are nonfoliated metamorphic rocks Examples : marble (made from limestone), quartzite (made from quartz - rich sandstone) SH1 63 1 02 Handout 1 *Property of STI student.feedback@sti. edu Page 11 of 11 NOTE : You can refer to Pages 2 - 4 of 02 Handout 2 for more information regarding the common rocks for each type of rock Reference s : Cortney (n.d.). Most common elements and oxides in rock - forming minerals Lifted and modified from https://www.luckysci.com/2014/05/most - common - oxides - in - rock - forming - minerals/ Geology In (n.d.). Cleavage of minerals . Lifted and modified from http://www.geologyin.com/2014/03/cleavage - of - minerals.html King, H. M. (n.d.). C rystal habits and forms of miner als and gems Lifted and modified from https://geology.com/minerals/crystal - habit/ Max Planck Gesellschaft (n.d.). Physical properties of minerals. Lifted and modified from https://www.mpp.mpg.de/~bangert/Mineralogy/physical_charac ter.html#Cleavage Minerals.net (n.d.). Mineral properties: Cleavage (including fracturing and parting) Lifted and modified from https://www.minerals.net/resource/property/cleavage_fracture_ parting. aspx Olivar, J. T. II, Rodolfo, R. S., & Cabria, H. B. (2018). Exploring life through science series: Earth science . Quezon City: Phoenix Publishing House. 27 - 47. Rocks for Kids (2018). How to Use Fracture and Cleavage for Mineral Identification? Lifted a nd modified from https://www.rocksforkids.com/fracture - cleavage - for - mineral - indentification/ University of Kansas (n.d.). Minerals Lifted and modified from http://people.ku.edu/~stalder/mineralogy.html