Clastic, Organic, Sedimentary Rocks (F2 Key Idea 1) Flashcards
What are the 3 Cs and 3 Ss?
Colour Size
Composition Shape
Cement or matrix Sorting
(refers to grains)
What does Maturity of a sediment refer to?
The degree of change in a sediment.
• Mature sediment has suffered more change than an immature one.
What is Cement and Matrix?
Cement - Binding material precipitated from moving solutions
Matrix - Relative finer grained sized sedimentary particles in between coarse grained particles
What are some common cements?
Red cement: Iron Oxide
Yellow and Brown cement: Hydrated Iron Oxides
White cement: Calcite*
- Effervesces in cold dilute HCl
What size are Coarse grains?
> 2mm
- If larger than 2mm, likely to be conglomerate.
• known as Rudaceous
What size are Medium Grains?
1/16mm - 2mm
• Known as Arenaceous
What size are Fine Grains?
<1/16mm
• >0.063mm = sandstone
• <0.063mm = mudstone
What is limestone and how do we classify it?
Often composed of materials that have a biogenic original rather than an inorganic origin, and contains >80% Calcite
Mineralogy: high % of calcite
Components: this can include fossils, oolites
Texture: Whether the crystals are large or small. It has crystals
Porosity: Can it hold water or oil. Limestone can
What is shelly limestone?
• Comprises mainly broken bivalve shells
• Is fossiferous
• Cement is calcium carbonate
• Reacts with dilute HCl acid
What is Oolitic limestone?
• Made up of spherical ooliths 0.5-1mm in diameter
• Reacts with dilute HCl
• Build up due to high energy wave action
How is coal formed?
• Plants grow, but they die and fall, forming separate layers.
• After many Ma, many layers have formed.
• The weight of the top layers, water, and soil compresses lower layers of plant matter.
• Heat and pressure produce chemical and physical changes.
• Oxygen is forced out leaving rich carbon deposits.
• In time, plant material becomes coal.
Key characteristics of peat coal?
• Semi-decomposed plant material
• Original vegetation structure still clearly recognisable
• Carbon content 50%
• Burns poorly, gives off much smoke
• Leaves behind a lot of ash
• Only burned where other fuels not available
• Rural areas – S. Ireland, N. Scotland
• Commonly decomposed in moors and wetland bogs
• Slow rate of decomposition; the fastest rate of decomposition is in nutrient rich water
Key characteristics of lignite coal?
• Carbon content 60-70%
• Darker brown colour than peat
• Woody look and ‘ring’ when tapped with fingers
• Generates much smoke and ash when burned
• Produces approx. 20kJ of energy per gram
• Density around 0.8g/cm3
Key characteristics of bituminous coal?
• Carbon content 80- 85% results in black colour
• Main type of coal mined in the UK
• Decomposition of plant material is complete = little evidence of original vegetation structure
• Breaks into cuboidal fragments and coal on your fingers
• Produces approx. 30kJ/g of energy when burnt
• Density of about 1.3 g/cm3
Key characteristics of anthracite coal?
• Contains 90-95% carbon
• No traces of original vegetation structure
• Burns slowly with hot, bright flame
• Gives off minimal smoke
• Leaves very little ash
• Black colour
• Vitreous to metallic lustre
• About 2 on Mohs hardness scale
• Can be iridescent
• Conchoidal fracture
• Does not soil the fingers when handled
• Produces around 34KJ/G of energy when burnt
• Has a density of about 1.5g/cm3
