Introduction to Mineralogy

• Mineralogy is a branch of geology focused on the study of minerals, their properties, and crystal systems

Key Terms in Mineralogy:

• Mineralogy: The study of minerals
• Mineral: A naturally occurring, inorganic solid with a specific chemical composition and crystal structure
• Morphology: The study of the shape and form of crystals
• Amorphous: Minerals lacking a definite crystal structure
• Massive: Minerals that are compact and without distinct crystal faces
• Crystalline: Minerals with a regular, repeating atomic arrangement
• Habit: The characteristic shape or appearance of a mineral
• Tenacity: A mineral's resistance to breaking or deforming
• Color: The visual appearance of a mineral
• Luster: The way a mineral reflects light
• Streak: The color of a mineral in powdered form
• Hardness: A mineral's resistance to scratching
• Cleavage: The tendency of a mineral to break along specific planes
• Fracture: The irregular breakage of a mineral
• Specific Gravity: The density of a mineral relative to water

Scope of Mineralogy:

• Crystallography: Focuses on the form and internal structure of minerals
• Physical Mineralogy: Focuses on the physical properties of minerals
• Chemical Mineralogy: Focuses on the chemistry of minerals
• Descriptive Mineralogy: Focuses on the classification and description of minerals

Earth's Crust Composition:

• Eight elements make up 98.59% of the Earth's crust by weight
• The remaining 100 elements constitute only 1.40% of the crust's weight

Mineral Formation and Characteristics:

• Minerals are found naturally and have a definite chemical composition and crystal system
• Minerals can be mostly solid, liquid (like mercury and water), or even organic
• Minerals generate rocks, and rocks constitute the Earth's crust

Importance of Minerals:

• Minerals are fundamental components of construction geology
• Minerals and rocks are essential for producing automobiles, construction materials, computers, and other products
• Minerals play a vital role in processes like landslides, coastal erosion, and volcanic activity
• Studying minerals and rocks provides insights into Earth's history and helps manage Earth's processes

Mineral Classification:

• Minerals are grouped into chemical classes depending on their chemical composition
• Classification is based on the dominant anion or anion complex

Anions in Mineralogy:

• Anion: A negatively charged ion attracting the anode in electrolysis
• Anion Complex: A compound anion consisting of multiple elements

Mineral Naming:

• There are approximately 4,150 known minerals
• 1,140 are silicates
• 624 are sulfides and sulfosalts
• 458 are phosphates
• 411 are oxides and hydroxides
• 234 are carbonates
• 90 are native elements
• Approximately 29% consist of carbonate, oxide, hydroxide, phosphate, sulfide and native elements
• Naming conventions weren't always scientific in the past

Mineral Name Origins:

• Quartz: From "Gangue", waste material in ore deposits, or "Spar", an old mining term
• Feldspar: Derived from the word "feldtspat
• Garnet: Derived from the Latin "granatum", resembling pomegranate seeds

Modern Mineral Naming

• The "Commission on New Minerals, Nomenclature and Classification" (CNMNC) sets the rules for naming new minerals
• Minerals may be named after their discovery location (e.g., Aragonite from Argon, Spain)

Crystal Morphology

• Crystal: A polyhedron form bounded by smooth surfaces, formed by chemical compounds under intermolecular forces
• Molecular Structure: Special arrangement of physical units called molecules during solid formation
• Crystalline: Has a definite molecular structure
• Amorphous: Lacks a definite molecular structure

Crystal Forms

• External Form: Described by faces or planes with symmetry related by mathematical laws
• Examples of crystal forms are galena, vesuvianite, and chrysolite
• Diversity of Forms or Habit: Crystals exhibit diverse forms, but angles between similar faces remain constant
• Habit(Shape) may vary indefinitely with changes in the relative size of faces
• Diversity of Size: Crystals range from microscopic to very large and development is complete regardless of size
• Symmetry in General: Crystal faces are arranged according to symmetry laws, defining crystal systems and classes

Crystal Symmetry

• Plane of symmetry: Symmetrical with reference to a plane for each face, edge, or solid angle ("mirror-image")
• Axis of symmetry: A solid of revolution through a certain number of degrees about an axis/line
• Binary of Twofold: Revolution of 180°
• Trigonal or Threefold: Revolution repeats 3 times, forming 120° angles
• Tetragonal or Fourfold: Revolution repeats 4 times, forming 90° angles
• Hexagonal or Sixfold: Revolution repeats 6 times, forming 60° angles
• Center of symmetry: Crystals lack plane or axis symmetry, but are symmetrical with reference to a center (e.g., Triclinic crystals)

Crystal Systems:

• Arrangement relative to length and inclination

Isometric System:

• Three equal axes at right angles
• Examples: Galena, Magnetite, Flourite, Pyrite, Sodalite, Leucite, Sphalerite, Garnet, Spinel, Diamond

Tetragonal System:

• Three axes at right angles, two horizontal axes (equal), vertical axis (longer or shorter)
• Examples: Zircon, Cassiterite, Wulfenite, Vesuvianite, Octahedrite, Braunite, Rutile, Chalcopyrite, Wernerite, Scheelite

Hexagonal System:

• Four axes, three equal horizontal, intersecting at 60°, a vertical axis at right angles
• Examples: Quartz, Beryl, Willemite, Corundum, Hematite, Chabazite, Tourmaline, Brucite, Calcite, Cancrinite

Orthorhombic System:

• Three axes at right angles, all different lengths
• Examples: Sulfur, Barytes, Stibnite, Staurolite, Aragonite, Calamite, Andalusite, Enstatite, Topaz, Anthophyllite

Monoclinic System:

• Three axes unequal in length, one intersection oblique (mono=single, clino=inclined)
• Examples: Gypsum, Orthoclase, Pyroxene

Triclinic System:

• Three unequal axes, mutually oblique intersections
• Examples: Albite, Rhodonite, Kyanite, Turquoise, Axinite, Microcline, Anorthite

Mineral Properties:

• Minerals can be identified by physical characteristics
• Physical properties relate to chemical composition and bonding
• Hardness: Very useful for identification
• Color: Though easily observed is usually not used for identification because it is not reliable

Mineral Tenacity:

• Describes mineral behaviour under deformation to externally applied stresses
• Crush, cut, bend and strike the mineral

Crystal Habit (Structure):

• Crystal form is useful to identify mineral
• Tabular: Elongated crystal that is flat

Crystal Habits

• Prismatic: Thin or thick elongated column-like crystals
• Lamellar: Flexible leaf-like sheets
• Radiating: Needle like which appears originating from a common point
• Granular: Densely packed mass of small grains
• Foliated: paper thin sheets
• Globular: Rounded overlapping bulb-like
• Reniform: Bulbs that resemble a kidney
• Mammillary: Projections overlapping a large size and rounded shape
• Fibrous: Composed of fibers generally separable
• Acicular: Needle like
• Dendritic: Tree-like branching

Color in Minerals:

• Color can be diagnostic and varies
• Idiochromatic: Fairly color relation to the composition of the mineral. Metallic minerals belong here.
• Allochromatic: Variable color due to colouring impurities
• Pseudochromatic: Shows false colour due to changes in refraction/reflection

Mineral Luster:

• Shine and reflection intensity from mineral surface
• Metallic: Shiny like metal
• Non-metallic: Adamantine (brilliant)
• Vitreous: Glassy looks
• Pearly: Iridescent pearl-like
• Silky: Fibrous with silk
• Resinous: Oily Shine
• Greasy: Waxy
• Dull: No Shine.
• Earthly: Dull like Clay

Mineral Streak:

• Color of finely powdered mineral

Mineral Hardness:

• Resistance to external deformation such as scratching, abrasion, rubbing or indentation
• Mohs Hardness Scale is used

Mineral Cleavage:

• Tendency of crystals to break along smooth planes

Terms Describing Cleavage:

• Number of directions
• Degree of splitting
• Perfection (eminent, perfect, good, distinct, indistinct)

Mineral Fracture:

• Describes the appearance of the broken surface of a mineral in a random direction

Types of Fractures:

• Even: Smooth and flat (e.g. limestone)
• Uneven: Irregular surface full of minute ridges (e.g. Beryl, Chromite)
• Conchoidal: Concentric rings or concavities (e.g. Obsidian, Agate)
• Splintry: Rough woody fracture (e.g. Serpentine)
• Hackly: Irregular with numerous sharp, fine projections (e.g. Copper)
• Earthy: Smooth, soft and porous (Limonite)

Specific Gravity:

• Diagnostic property relating the density of a mineral to water

Other Identifying Characteristics:

• Minerals have unique properties based on composition that we can use to identify them
• Minerals give off a certain smell and taste

Mineral Formation & Processes:

• Minerals form under geological conditions
• Minerals can form from crystallization of magma, deposition from a saline fluid, volcanic gases, sediment formation, oxidation
• Minerals that become part of rock formations are known as rock-forming minerals

Mineral Resources:

• If the minerals found in rocks are rich with one or more useful materials, they are mineral recourses
• Mineral resources must go through geological principles

Ore in Mineralogy:

• A naturally occurring solid material where metals are extracted from