Chapter II: Rock-Forming Minerals and Rocks Flashcards
What traits of minerals determine their physical properties?
Hardness is determined by the strength of the chemical bonds.
Density is determined by the weight of its atoms, and to some degree their structure.
Fracture Pattern is determined by the weakness of the crystalline structure.
What conditions produce various kinds of igneous rock?
Mafic igneous rocks are denser than felsic rocks due to the high atomic weight of iron atoms. Extrusive rocks are smooth due to their rapid cooling, conversely intrusive rocks are more granular due to their slow cooling.
What are the ways in which sedimentary rocks form?
Clastic sedimentary rocks form when sediments are deposited then compacted by the weight of sediments above them. Next they are cemented by fluids, causing minerals to precipitate and form the rocks.
Chemical Sedimentary rocks form when they are precipitated from water.
How do metamorphic rocks form from other rocks?
Composition and texture vary depending on degree of heat and pressure. 4 methods of metamorphism; Regional, Contact, Hydrothermal, and Burial.
How does an ion form from an uncharged atom?
Ions are formed when an uncharged atom gains or loses an electron(s) in order to form a more stable valence shell.
Silicates
Most abundant mineral family in Earth’s crust/Mantle. Basic building block of SiO4
Sedimentary Structure
Distinct arrangement of grains which reflects the method of deposition.
Why do most sediments formed by weathering consist of silicate minerals?
Because silicates make up the majority of rocks on earth.
Silliclastic Sedimentary Rocks
Consists of silicate grains produced by weathering and erosion
Regional Metamorphism
generally within hundreds of kilometers, caused by catastrophic events such as a meteor impact which creates the conditions necessary for metamorphism.
Contact Metamorphism
heat from an igneous intrusion bakes surrounding rock
Hydrothermal Metamorphism
hot, watery, fluids percolate through rocks to form metamorphic rocks
Burial Metamorphism
Deep burial of rocks produces the conditions necessary for metamorphism (i.e. Coal from plant material)
Ions
Retain their identity when dissolved in water. Enables chemical precipitates like salt.
Aragonite
Common minerals consisting of calcium carbonate (CaCO3);
Precipitates directly from shallow tropical seas as tiny needle shaped crystals and accumulates into carbonate mud.
Forms younger Limestone because it is unstable.
Calcite
Common mineral consisting of calcium carbonate (CaCO3);
Precipitates to form blocky, or tooth shaped crystals. Forms Limestone that can last much longer than Aragonite based Limestone.
Calcite
Common mineral consisting of calcium carbonate (CaCO3);
Precipitates to form blocky, or tooth shaped crystals. Forms Limestone that can last much longer than Aragonite based Limestone.
8 Major Mineral Groups
Silicates, Carbonates, Sulfates, Phosphates, Halides, Oxides, Sulfides, Native Elements.
Silicates
(SiO4)^-4 tetrahedra are basic units;
Mostly hard, except for mica and clay minerals, glassy/pearly luster;
Dominant mineral group in crust and mantle;
Carbonates
Positive Ions attached to (CO3)^-2;
soft, light colored;
Mostly sedimentary, but also marble (metamorphic);
Sulfates
Positive ions attached to (SO4)^-2;
Soft, light colored, water soluble;
Mostly sedimentary
Phosphates
Positive ions attached to (PO4)^-3;
soft, weakly soluble;
relatively uncommon sedimentary rocks;
Halides
Positive ions attached to negative ions;
soft, light colored, water soluble;
most rock forming halides are sedimentary;
Oxides
Metallic ions combined with oxygen;
soft to hard;
mostly sedimentary but many varieties present in crystalline rocks;
Sulfides
Metallic ions combined with sulfur;
Soft to medium hard, often metallic;
minor role in rock forming, many precipitate;
Native Elements
Pure forms of elements;
variable physical properties;
forms graphite through metamorphosed organic carbon;
Dolomite
Similar to Calcite, but calcium ions are replaced with magnesium ions. Special layered crystalline structure. Not secreted by any organism in the form of a skeleton.
What allows one element to substitute for another in the crystal of a particular mineral?
Elements can substitute for each other if both atoms have a similar charge and size.
Dikes vs Sills
Sills are plutons which are injected between sedimentary rock while dikes cut upwards between layers of sedimentary or crystalline rock
Plutons
another word for intrusive rock
How does the origin of clay particles differ from the origin of sand particles from the same rock
Clay is formed from chemical weathering while sand is formed from physical weathering.
Shale formation vs Sandstone formation
Shale can only be formed in calm water because clay settles so slowly. Sandstone forms in moving water because sand settles more quickly.
Graded beds
Formed by swift currents with varying sediment size. Coarser sediment settles more quickly than finer sediments.
Ripples
equal slopes, formed by the motion of waves
Cross-Beddding
Uneven slopes, steeper on the backside, side facing away from current. Formed by water or air currents
Mud Cracks
Formed when mud is deposited in shallow, calm water. Water evaporates leaving mud exposed and further evaporation leaves cracks as the mud dries.
Why do evaporites weather so quickly?
Due to their solubility in water, evaporites last above the surface for an extended time only in arid climates.
Basalt
Formed when lava flows slowly out of a fissure rather than a vent
Vent
Exposure to the surface from which lava forms volcanoes
Pillow Basalt
Basalt formed under the sea. Rapid cooling gives its surface a hummocky configuration
Pumice
Frothy lava from a high velocity eruption, glassy and very light (often floats on water)
Tuff
sedimentary rock formed from volcanic material
Gneiss
High quality metamorphic rock, crystals resemble igneous rock
Schist
low to medium grade metamorphic rock, largely grains of platy material including mica
Foliation
alignment of platy materials caused by pressures applied during metamorphism
Slate
very low grade metamorphic rock.
Bioturbation
disturbance of sedimentary bedding by the activity of animals
peat
leafy and woody plant tissue accumulated in oxygen deprived water, the starting material for coal
Oolites
sediments or rocks consisting of nearly spherical grains
Intraclsts
Fragments of preexisting seafloor material that gets ripped up by storms or other sudden events
Fecal Pellets
sand sized grains found in carbonate mud which have passed through the guts of invertebrate organisms
Coal
rock formed by stratified plant debris, can be burned because more than 50% organic compounds
Clasts
fragments of rock produced by destructive processes
