Mineralogy and Petrology Review

Flashcards covering key concepts in mineralogy and petrology for exam review.

What is a mineral?

N.I.S.C.Cis an acronym that stands for "Natural, Inorganic, Solid, Crystalline, and Chemical composition". This classification helps to define the essential characteristics of minerals.

What are some examples of non-minerals?

water, coal, pearl, gas, ice, wood; obsidian (no crystal structure)

What are the primary physical properties used to identify a mineral?

Habit (shape); cleavage (break points); luster (reflects light); streak; specific gravity; hardness; color, taste, smell, feel, magnetism, chemical reaction (HCl on limestone).

What does growth rate control about a mineral?

How fast you can add things onto the crystalline lattice.

What is a Euhedral crystal?

Crystal faces are flat and fully developed.

What is a Subhedral crystal?

Imperfectly developed crystal faces.

What is an Anhedral crystal?

Without developed crystal faces.

What does crystallization from melts and vapors usually require?

Usually requires some undercooling.

What does crystallization from aqueous solutions usually require?

Usually requires supersaturation.

What is a Unit Cell?

The smallest divisible unit of a mineral that possesses the symmetry and properties of the mineral.

How does a unit cell affect mineral properties?

Stacking of unit cells leads to the regular repeated pattern of a mineral.

What is a Native Element mineral group?

No anion, pure elements - gold.

What is a Sulfide mineral group?

Metal + S - pyrite.

What is a Sulfate mineral group?

Metal + SO4 - gypsum.

What is a Oxide mineral group?

Metal + O – hematite.

What is a Halide mineral group?

Metal + Cl, F, Br – halite.

What is a Hydroxide mineral group?

Metal + OH

What is a Carbonate mineral group?

Metal + CO3

What is a Phosphate mineral group?

Metal + PO4 – apatite.

What is a Silicate mineral group?

Metal + Si and O – quartz.

What are some examples of 'Other' mineral groups?

Borates, urananates.

What is an atom?

The basic, neutral form of an element; Number of protons = number of electrons; It has no overall charge.

What is an ion?

An atom that has gained or lost electrons, giving it a charge.

What is a Cation?

Positively charged – loses electrons.

What is an Anion?

Negatively charged – gains electron.

What is a shell (when referring to an atom)?

A layer around the nucleus of an atom where electrons are found; also called energy levels.

What electron configuration makes an atom willing to gain or lose electrons?

Atoms ‘want’ a full outer shell; Easier to lose electrons if there are only 1-3 in the outer shell; Easier to gain electrons if there are 5-7 in the outer shell.

How does Atomic Size dictate if an atom gains or loses electrons?

Larger atoms (lower in the periodic table) hold onto outer electrons more loosely; Easier to lose electrons.

What is Electronegativity?

How strongly an atom attracts electrons.

High electronegativity --> ?

More likely to gain electrons.

Lower electronegativity --> ?

More likely to lose electrons.

What happens to an atom when it forms a Cation?

Shrinks, the pull from the protons become stronger so the remaining electrons are pulled closer to the nucleus, more stable.

What happens to an atom when it forms an Anion?

Extra electrons cause more repulsion among them → atom gets larger; Positive pull from the nucleus is weaker; More stable.

What are Ionic Bonds?

Ions that have very different electronegativity values; the more electronegative element will attract an electron to the outer shell (ex. Na Cl).

What are Covalent Bonds?

Ions that have similar electronegativity values; atoms share electrons so that the outer orbitals overlap (ex. Si and O).

What are Metallic Bonds?

Bond with loosely held electrons in the outer shell that are free to travel from one atom to another.

What are Van deer Waals Bonds?

Bond between structural units as a result of small residual charges on their surfaces.

What are Hydrogen Bonds?

Polar molecules form crystalline structures by attraction between oppositely charged ends of molecules.

What properties do Ionic Bonds impart on a mineral?

High melting point, moderate hardness – halite.

What properties do Covalent Bonds impart on a mineral?

High melting point, higher hardness, strongest bond type – sulfur.

What properties do Metallic Bonds impart on a mineral?

Malleable, ductile, soft, metallic luster, dense structure – native gold.

What properties do Van der Waals Bonds impart on a mineral?

Weakest bond type, clay, graphite.

What is coordination number? How is it determined?

Ratio between a cation and anion size, bigger difference between the two, the lower the coordination number (only get two ions to touch the central ion = 2), as the central atom gets bigger you can add more touching around it, higher the coordination number.

What are Pauling's Rules?

Why minerals are going to come together

Charge balance needs to be maintained – the right charge

Does a particular cation or anion fit within a lattice - the right size.

Wha is Direct Subsitution?

1 to 1 replacement of atoms

What is Coupled Substitution?

Involves complex mechanisms where a substitution reaction is coupled with another reaction or step, such as a redox reaction.

What is Limited Substitution?

Only one or a specific number of substitutions happen.

What is a Crystal?

A solid where the atoms, ions, or molecules are arranged in a highly ordered repeated pattern that extends in all directions; Gives them distinct shapes, like cubes or hexagons.

What is Crystallography?

The study of crystal structures of how atoms are arranged inside a solid.

How does a unit cell relate to crystal shape?

Helps determine the overall shape of the crystal, its symmetry, angles and lengths of the crystal faces.

What is Symmetry?

Balanced, repeating patterns found in the crystal’s internal structure and external shape.

What factors determine the growth of mineral faces?

Shape of unit cell (how close together atoms would be), how easy is it to add material in one direction.

What are the 2-D symmetry types?

Rotational, reflection, translational, glide.

What are the 3-D symmetry types?

Rotational, mirror, inversion centers, rotoinversion axes, translational.

How are 2-D and 3-D symmetry types similar?

Patterns repeat (unit cells repeat); around a point (around an axis); across a line (across a plane); left-right, up-down (in all three directions).

What is a Motif?

The think being copied during the pattern formation.

What is an Operation?

The action or movement that places the motif in a new position without changing the appearance.

What is an Element?

The imaginary feature or point/line/plane about which the symmetry operation happens.

What are the 6 crystal systems?

Cubic (isometric) (equal)

tetragonal (stretched cube)

orthorhombic (sides different lengths – right angles)

monoclinic(most right angle and one slanted)

triclinic(no equal lengths or angles – most distorted)

hexagonal(two equal sides in a flat plane – third axis is different and vertical).

What are Miller Indices used for?

A way of addressing a particular shape.

find the biggest face - different axis

biggest face is the starting point

shows where you are in relation to the crystalline axis

What is a silica tetrahedron?

Basic building block of all silicates (4 oxygens and a silica in the middle) (pyramid).

What is the Tetrahedron Arrangement for Nesosilicates (Isolated Silicates)?

Tetrahedra are not connected to each other; each stands alone; Olivine, garnet.

What is the Tetrahedron Arrangement for Sorosilicates (Double Tetrahedra)?

Two tetrahedra share one oxygen atom; Epidote, vesuvianite.

What is the Tetrahedron Arrangement for Cyclosilicates (Ring Silicates)?

Tetrahedra are linked in rings; Beryl, tourmaline.

What is the Tetrahedron Arrangement for Inosilicates (Single Chain Silicates)?

Tetrahedra form single chains by sharing 2 oxygens; Pyroxene group.

What is the Tetrahedron Arrangement for Inosilicates (Double Chain Silicates)?

Tetrahedra form double chains; alternating sharing of 2 or 3 oxygens; Amphibole group.

What is the Tetrahedron Arrangement for Phyllosilicates (Sheet Silicates)?

Tetrahedra form sheets, sharing 3 oxygens each; Mica, talc, clay minerals.

What is the Tetrahedron Arrangement for Tectosilicates (Framework Silicates)?

Each tetrahedron shares all 4 oxygens → 3D framework; Quartz, feldspar, zeolite.

Why are silicates arranged in groups?

Grouped based on how their silica tetrahedra are arranged and bonded; Affects: 1. Overall crystal structure 2. Physical properties 3. Chemical behavior.

Which silicate groups tend to have examples that accept lots of different elements into their crystalline lattice?

Nesosilicates (leaves room for variation); inosilicates (open spaces); tectosilicates (can accept various metal cations).

Which silicate groups tend to have examples that DO NOT accept lots of different elements into their crystalline lattice?

Cyclosilicates (rigid); sorosilicates (limited substitution); phyllosilicates (moderate substitution possible, but layers limit the size/type of ions.

How is an index of refraction found?

It is found with the formula n=c/v; C is the speed of light in a vacuum and v is the speed of light in the medium in question; C=2.998x10^8 m/s or 3.0x10^8 m/s.

What is the relationship between velocity of light and index of refraction?

The index of refraction is inversely proportional to the speed of light in a material.

Relate wavelength to what we see and its energy in the electromagnetic spectrum.

Visible light is a small space in the electromagnetic spectrum that we can detect with our eyes. It goes from about 380nm to 700 nm. 380 nanometers is violet light and 700 nanometers is red light. Shorter wavelengths = higher energy; longer wavelengths = lower energy E=hc/λ

What is the difference between an isotropic and anisotropic mineral?

Isotropic minerals have the same optical properties in all directions and anisotropic minerals have different optical properties depending on the direction the light passes through them, meaning they will have different colors as you rotate them.

What is extinction and why does it happen?

It is when part of a mineral under a microscope disappears or goes dark when rotating it. This happens when cross-polarized light dims as viewed through a thin section of a mineral.

What is birefringence?

Also called double refraction. The optical property of a material having a refractive index that depends on polarization and propagation direction of light. They are optically anisotropic as well.

Understand what relief is and how to figure it out

It is used to describe the degree to which edges and surface imperfections of crystals are visible in plane-polarized light. A mineral has high relief when it has sharp boundaries between itself and the material it is next to. Low relief is when the mineral has ‘weak’ or hard to see edges.

Where are magmas at different plate settings sourced from? Ocean Island, Mid-Ocean Ridge, Island Arc, Continental Flood Basalts, Layer mafic intrusions, continental arc magmas, etc.

• Mid-Ocean Ridges (MOR): divergent plate boundaries (oceanic-oceanic) – comes from shallow upper mantle (depleted asthenosphere)
• Ocean Island Basalts (OIB): intraplate, above a mantle plume or hotspot (Hawaii) – comes from deep mantle/plume head, maybe from near the core-mantle boundary)
• Island Arc Magmas: subduction zone (oceanic-oceanic) (Japan, Aleutians) – mantle wedge above subducting slab
• Continental Arc Magmas: subduction zone (oceanic-continental) (Andes) – mantle wedge + continental crust
• Continental Flood Basalts (CFBs): intraplate, linked to plume heads or rifting (Siberian Traps) – comes from asthenosphere plume source, possibly involving melting of lithospheric mantle too
• Layered Mafic Intrusions: continental rifting or plume-related magmatism (Skaergaard) – mantle-derived basaltic magmas

Know what depleted vs. enriched mantle is

Depleted means that it has been melted before and it becomes more mafic and a less chemically rich source (tea); Enriched is fresh or recharged mantle meaning it is either less melted or had extra elements added back in (brand new tea bag or used with extra syrups added in)

Know what plate tectonic settings produce what kind of volcanoes/lavas/plutons/magmas

• Mid-Ocean Ridge: submarine fissures – basalt (MORB) – gabbro
• Island Arc: stratovolcano – basalt → andesite (hydrated) – diorite, tonalite
• Continental Arch: stratovolcano – andesite → rhyolite – granite, granodiorite
• Oceanic Hotspot: shield volcano – basalt (alkaline/tholeiitic) – small mafic bodies
• Continental Hotspots/CFB: fissures/floods – basalt → rhyolite – mafic intrusions syenite
• Continental Rift: domes, fissures – basalt to rhyolite – syenite, granite
• Transform Fault: none – N/A – N/A

Know the difference in behavior between different magmas/lava and why this is. Mafics vs. Felsics

Mafic magmas are characterized by low silica content leading to low viscosity and primarily form basalt, resulting in effusive eruptions. In contrast, felsic magmas have high silica content, which increases viscosity, leading to explosive eruptions and typically forming rhyolite.

Felsic (rhyolite): High silica content, Light (white, pink, light gray) color, High viscosity (thick, sticky) Cooler (~650-800C0, Higher gas content, Explosive eruption style (gas gets trapped), Quartz, feldspar, biotite, muscovite crystal content, Domes, stratovolcanoes, calderas volcano shape

Understand what volatiles are

They are gases dissolved in magmas. The main ones are water vapor, carbon dioxide, sulfur dioxides (H20, CO2, SO2) and the minor ones are H2, Cl, F, etc. They are dissolved under pressure but they come out as bubbles when the pressure drops.

How do volatiles affect melt properties?

More volatiles = easier to melt rock

How do volatiles affect viscosity?

Indirectly, they can temporarily lower viscosity (when still dissolved), making more magma more mobile and once they start forming bubbles they can increase viscosity again

How do volatiles drive magma ascent?

Bubbles expanding can increase the magma’s buoyancy and accelerates magma upward, increasing eruption chances

Volcanic cone magma type

Rhyolite

Cinder cone magma type

Mafic and have gas; blows out

Shield volcano magma type

Mafic lavas, pour out of the central vent or secondary vent or flank; pile of basalt

Stratovolcano magma type

Felsic, mafic, maybe intermediate, steep

What about a rock system needs to change to produce melting?

Increase the temperature – hotspots, under large intrusions, continental collision zones; Decrease pressure (decompression melting); as a rock moves towards the surface the pressure drops faster than it cools – happens at mid-ocean ridges, continental rifts, and hotspots; Add Volatiles (flux melting); adding water or CO2 lowers the melting point of rocks – happens at subduction zones

How do you get a rock system to change to produce melting?

Increase the temperature, decrease pressure (decompression melting), add Volatiles (flux melting)

Why are pegmatites weird?

They have giant crystals – can have ones meters long; Chemical Extreme – form last and are enriched in rare elements like lithium, beryllium, boron, cesium, tantalum, uranium and will have tourmaline, spodumene or lepidolite sometimes; can be zoned and crazy complex; layered like a cake, quartz core, a wall zone with feldspar, weird mineral pockets – can be used for elements critical for batteries and tech

What are Dikes?

Cuts across existing rock layers, steeping dipping or vertical, often narrow but long, magma forces its way inter fractures

What are Sills?

Parallel to bedding or foliation, form between layers of rock, typically horizontal or gently inclined

What are Laccoliths?

A sill that bulges upward, forming a dome shape, magma is viscous and pushes overlying layers upward

What are Lopoliths?

Concave-downward intrusions, huge and often fed by multiple dikes/sills, mafic to ultramafic in composition

What are Batholiths?

Massive intrusions, composite bodies, often associated with continental arcs, represent magma chambers that never erupted

What are Plutons?

Generic term for any intrusive igneous rock body, can be part of batholiths or individual intrusions

How do magmas diversify?

Fractional Crystallization; Partial Melting; Magma Mixing; Assimilation