Rock Types

Rock Types  

Igneous  

Sedimentary  

Metamorphic  

Igneous Rocks 

Christianized/solidify from a magma or lava  

When you have melted rock, that is at the bottom of the volcano is magma but at the surface its lava 

Classification based on texture and composition  

Texture: Course-Granted, Fine Grained, Porphyritic, Vesicular, Glassy, Pegmatitic, Pyroclastic  

Rocks are bad at changing heat. If the manga chamber took a long time to cool, it would be coarse- grained.  

High Sio2         Composition Low Sio2 

The darker the rock the less Sio2 

The lighter the rock is more Sio2  

Glassy- Eruption in water; Obsidian  

Pegmatitic (>1in) Pegmatitic  

Vesicular (Bubbly) More Gas bubbles Pumice  

Less Gas bubbles Scoria (Swiss Cheese Look)  

Pyroclastic  

Ash-sized = Tuff (Strong Building Mineral) 

> Ash = Volcanic Breecia  

Igneous Rocks  

Composition  

Ultramafic- Olivine and Pyroxene 

• Mostly in Mantle  

Mafic- Pyroxene and Plagioclase

±±

Olivine 

• “Dark” colored 

Intermediate- Amphibole/ Biotite/Muscovite Plagioclase  

• Generally, "light” colored  

• If Quartz/K-feldspar is visible it is felsic even if otherwise dark  

Igneous Differentiation  

Different minerals have different crystalize properties 

• Partial Melting 

Assimilation  

Liquids goes towards more Felsic  

Sedimentary Rocks  

Detrital  

• Broken bits of things  

• Similar to Concrete 

1. Deposition  

2. Compaction (Going to Lake) (Keep building) 

3. Cementation 

Classification 

• Size of the grains, and how big are those bits, and shape 

Coarse grained has to be bigger than 2mm (Bigger than the thickness of a nickel)  

Rounded Angluar  

Chemical Sedimentary Rocks  

Crystalline LS = Mirco-crystalline calcite  

Ocean Components  

The process is completely inorganic process  

Coquina = oatmeal cookie (Layers of shells) 

Fossiliferous LS = Fossils + Crystalline LS  

Chalk = Tiny shells  

Chert (Flint)  

Harder than Chalk even though its the same material, composed of silica from diatoms  

Organic Sedimentary Rocks  

Coal  

• Compacted organic material - typically plants 

• Various grades based on amount of compaction and heat/pressure  

• Typically, black with low density 

Metamorphic Rocks  

There must be a preexisting rock, and it must be out of equilibrium  

Non- equilibrium reaction (that change will be  

The rock is equilibrium of that environment  

Heat and Pressure drives Metamorphism (Increases Heat and Pressure)  

Pressure changes the texture and how it looks  

Temperatures naturally increase= 

Chemically active fluids 

Classification by texture  

The primary source we are looking at is texture.  

Is the rock in foliation= any sort of “preferred” alignment  

Nonfoliate  

• Composition 

• Marble – Calícate(Can do the Acid test)  

• Quartzite- Quartz (Sandstone protolith)  

Foliated  

• Slate –Low Grade 

• Phyllite – Low/Medium grade 

• Schist – Medium Grade 

• Gneiss – High Grade