Mineral Properties and Identification

• Here are study notes compiled from the provided mineralogy text.

Mineralogy Basics

• Mineralogy studies minerals' structure, chemical, crystalline properties, physical attributes, origins, formation, classification, distribution, uses.
• Minerals are naturally occurring, inorganic, solid elements or crystalline compounds.
• Minerals have a defined atomic structure and chemical composition.
• Over 4000 minerals exist in the Earth's crust.
• All minerals are composed of oxygen, silicon, aluminum, iron, calcium, potassium, sodium, and magnesium.

Mineral Classifications

• Rock-forming minerals are abundant in the Earth's crust and form igneous, sedimentary, or metamorphic rocks.
• Ore-forming minerals have economic value, a limited occurrence, and are formed by unusual processes.
• Oxides contain O2- anions, with exceptions like carbon, sulfur, and silicate.
• Sulfides contain S-2 anions.
• Sulfates contain SO4-2 anions.
• Halides contain halogens like F, Cl, Br, etc.
• Carbonates contain CO3-2 complex anions.
• Phosphates contain PO4-3 complex anions.
• Silicates contain Si:O2 or Si:O4, with combinations of silicon and oxygen.
• Native minerals consist of single elements.

Mineral Physical Properties

• The color of minerals is not constant and can be affected by stains or impurities.
• Color may indicate that a mineral has undergone peculiar phenomena.
• The "play of colors" is the development of prismatic colors when light turns.
• Change of colors is similar to the play of colors but with slower rotation.
• Iridescence shows rainbow colors on the interior or surface of the mineral.
• Streak: Color of mineral powder, nearly constant.
• Streak is determined by marking unglazed porcelain with a knife and observing the powder color

Luster and Habit

• Luster is the description of how much a mineral reflects light.
• Metallic (shiny) lusters are glassy (vitreous) like broken glass, metallic like metal, or pearly like pearls.
• Nonmetallic (dull)
• Structure and form (habit) denote the shape and form of minerals.
• Prismatic shapes are elongated in one direction like a prism.
• Tabular shapes are like a table or plate.
• Equant possess approximately same side length in every direction
• Foliated structures are in thin sheets, flakes, or scales.
• Fibrous structures are crystal aggregates resembling long, slender needles, hair, or threadlike fibers.
• Reticulated structures are aggregates of crystals forming a network or lattice.
• Stellated structures are composed of branches radiating star-like from a central point.
• Dendritic structures have divergent branching like a tree, representing mineral growth.
• Columnar or stalactitic structures are thick or thin column-like structures.
• Micaceous structures are thin, flat sheets or flakes that easily peel or split off a larger mass.
• Acicular structures contain many long, slender crystals that radiate like needles or bristles from a common base, similar to a pine leaf.
• Filiform structures exhibit many hair-like or threadlike filaments.
• Hopper structures have fully developed edges, but interior spaces are not filled, leaving them hollow.
• Plumose structures have fine, feathery scales resembling plumes.
• Bladed structures are blade-like, elongated, with flat crystals like knife blades.
• Radiated structures have fibrous diverging from central points.
• Lamellar structures are made of separable plates, feathery or delicate aggregates.
• Colloform structures are spherical, rounded, or bulbous shape.
• Botryoidal structures are an aggregate-like bunch of grapes or globular shape.
• Reniform structures are kidney-shaped aggregates.
• Mamillary structures display soft, rounded curves.
• Striated structures display shallow parallel grooves or lines along flat crystal faces.
• Granular structures are densely packed grains.
• Massive structures have no definite shape, are large and lumpy

Mineral Properties and Behavior

• Hardness measures resistance to abrasion or scratching and is relative to a scale of ten minerals.
• Specific gravity is the mineral's density compared to the density of water. Metallic minerals have high specific gravity; non-metallic minerals have low specific gravity.
• Cleavage is the tendency of a crystallized mineral to break along certain definite planes, yielding smooth surfaces.
• Cubic: 3 cleavages
• Octahedral: 4 cleavages
• Dodecahedral: 6 cleavages
• Basal: 1 cleavage
• Fracture is the appearance of a mineral's broken surface.
• Conchoidal fractures have concentric rings or curved surfaces.
• Even fractures are smooth and flat.
• Uneven fractures are irregular.
• Splintery fractures break with a rough appearence.
• Tenacity is the behavior of a mineral when deformed or broken.
• Sectility: Minerals may be cut with a knife
• Malleability: A mineral may be pounded out into thin sheets.
• Brittleness: A mineral breaks or powders easily.
• Elasticity: Regains its former shape as pressure is released
• Ductility: A mineral may be drawn into a wire; tough as well
• Plasticity: A mineral will stays deformed when released

Crystallography and Systems

• Crystallography studies the formation, properties, and structure of crystals and deals with geometric forms.
• Mineral crystal system, also called mineral habits, are arrangements of crystal forms within a specific mineral (e.g., Diamond: two pyramids at their bases. Quartz: six sides).
• Crystal forms: Internal atomic arrangement of mineral manifested outwardly by geometrical shapes or crystal characters.
• Crystallized minerals occur in defined crystals.
• Amorphous minerals show no signs or evidence of crystallization.
• Crystalline minerals lack well-defined crystals but have a tendency towards crystallization.
• Symmetry and lattices describe the repetition of structural features.
• General Types: Symmetry- Describes the repetition of structural features - 2 GENERAL TYPES:
• Translational: Periodic repetition of a structural feature across a length or through an area or volume.
• Point: Periodic repetition of structural feature at a point. Reflection, rotation, and inversion apply.
• Lattices are directly related to translational symmetry.
• Lattices: Network/array of single motif that repeats at fixed intervals in space.
• Bravais lattices have fourteen different arrangements in 3D space divided into six crystal systems and three types: Primitive, face-centered, body-centered.
• Crystal systems are defined by a combination of three factors.
• Number of axes
• Length of axes
• Angles at which axes meet
• Axis A is usually the shortest, while C is the longest axis
• Set of faces that are geometrically equivalent and whose spatial positions are related to one another according to symmetry.
• Each crystal system can obtain different crystal forms.
• Crystal form types: Monohedron, Parallelohedron, Dihedron, Disphenoid, Prism, Pyramid, Dipyramid, Trapezohedron, Scalenohedron, Rhombhohedron, Tetrahedron.
• Crystal System Examples: Isometric, Tetragonal, Orthorhombic, Monoclinic, Triclinic, Hexagonal

Mineral Groups

• Quartz Family:
• "Quarz” means uncertain origin
• Word crystal originaly used only for quartz
• Rock former next to feldspar
• Non-metallic refractory mineral with high melting points
• A member of the SILICATE mineral group
• Chemistry: Chemical Formula: SiO2, Molecular Weight: 60.08 g
• Composition: Silicon: 46.74%, Oxygen: 53.26%
• Formation: Formed by crystallization of silica-rich molten rock (magma) in pegmatites, in hot watery solutions (hydrothermal environments) between 100 - 450C under high pressure.
• Physical Properties: Crystal System: Hexagona;. Habit: Crystalline or Armophous; Cleavage: Indistinct; Fracture: Conchoidal; Color: Pure - Colorless, Colored - indicate impurities; Luster: Vitreous; Hardness: 7; Tenacity: Brittle; Specific Gravity: 2.6 - 2.7; Streak: White; Transparency: Transparent/ Semi-transparent/Opaque
• Polymorphic Transformation: Quartz, tridymite, cristobalite, moganite, coesite, keatite
• Occurrence: Mostly found in igneous, sedimentary and metamorphic rocks
• Use: Glassmaking industry

Feldspar Family

• Feldspar Family: "Feldspat" meaning in german "a rock that does not contain a core"
• Most abundant of all minerals, composing over 50% of earth's crust by Weight.
• Non-metallic and silicate
• Chemical Formulas
• Plagioclase: Na Al Si3O8
• Potassium Feldspar (Alkali Feldspar): KAl Si3O8
• (or Soda-lime Feldspar) Ca Al2 Si2O8
• Occurence: Crystallize from magma, are present in many metamorphic and sedimentary rocks
• Use: Raw Materials uses in glassmaking/ceramics/filler plus extender in paint/plastics/rubber. Alumina from feldspar improves product hardness/durability/resistance to chemical corrosion. Act as flux to lower melting temperatures.
• Plagioclase Physical Properties: Crystal System: Triclinic Habit: Tabular (Crystalline); Cleavage: Perfect - 2 Directiona; Fracture: Conchoidal
• Orthoclase: a member of the alkali feldspar, Crystall System: Monoclinic, fracture: uneven/conchoidal, transparent to transparent

Pyroxene Group

• Important group of rock forming minerals, usually occuring in dark colored igneous/metamorphic rocks and rich in calcium/magnesium/iron/silicates. Show a single chan structure of sliccate
• Classified intro Orthopyroxene(Enstatite Mg SiO3, Hyperthene: (Mg, Fe) SiO3) and Clinopyroxene Augite, Diopside and Hedenberguite
• Physical Properties:
• Crystal System: Monoclinic
• Habit: Crystalline
• Cleavage: Good(prismatic)
• Luster: Vitreous ,dull on other surfaces
• Specific Gravity: 3.2to 3.6, traslucent/Opaque, brittle
• Occurrence: Ferro magnesium mineral of igneous rock, in mafic and intermediate igneous rocks basalt, gabbro,andestite,diorite

Hornblende

• a complex inosilicate series of minerals.
• The General formula: (Ca,Na)2-3(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2
• Physical Properties: Crystal System: Monoclinic,
• Habit: Hexagonal, granular,imperfect cleavage, uneven fracture, color: black, dark Green to brown

Mica Group

• Form sheet like structure, splitting into very thin sheets
• Rich in Aluminum and magnesium
• Occupy 4% of earth's crust
• Mica - Biotite
• Group of black mica minerals, with Chemical Composition of K(Mg, Fe)3(Al Si3)O10(F, OH)2
• Physical Properties: Crystal System: Monoclinic, prismatic, Massive to platy Basal
• Mica- Musovite
• Most common of the Mica Family wich has a chemical compostition; KAI2(Si3AIO10)(OH)2, cristal sysyem monoclicmassive/paty, perffect cleavage, micaceous structure and fracture

Calcite and Garnets

• Calcite: A rock forming mineral considered ubiquitous, a pricipal constituent of limestone/marble and carbon repository. Chemical formula: CaCO3. Crystal System: Hexagonal, rhombohedral, perfect cleavage and conchoidal fracture
• Garnet Family:
• Rock forming minerals
• Share crystal structure and chemical compostition
• Chemical formula: X3Y2, X= Calcium, Magnesium, iron, Y = Aluminum, Iron, Manganese
• Most common in metamorphic-few are found on igneous rocks, for gems, crush garnet for abrasives

Explore mineral properties like specific gravity, habit, and symmetry. Understand mineral composition, economic value, and factors influencing color. Test your knowledge of mineral identification techniques, including streak and luster.