Lecture Sixteen Flashcards
Define a rock.
A coherent, naturally occurring solid, consisting of an aggregate of minerals or less commonly, a mass of glass. Coherent = sticks together, but can be broken into pieces. Naturally occurring = not bricks or concrete. Aggregate of minerals or mass of glass - most rocks are made of minerals, a few volcanic rocks are made of rapidly cooled glass.
Define a mineral.
A mineral is a naturally occurring homogenous solid with a definite (but generally not fixed) chemical composition and an ordered atomic arrangements. It is usually formed by inorganic processes.
What do the properties of minerals depend upon?
The types of atoms present (elements, oxidation states). The geometrical arrangement of the atoms (crystal structure). The bonding forces between the various atom pairs and structural units.
What are the ionic and valance states of the atoms in rocks?
Atoms in minerals are often considered as ions (charged particles) - especially for minerals with ionic bonds. Minerals are electronically neutral. Common rock-forming ions: H+, Na+ and K+ Mg2+, Ca2+ and Fe2+ Al3+ and Fe3+ Si4+ and C4+ O2-, S2-, S6+ and Cl-
How does the packing of atoms in a crystalline structure work?
Most minerals are ordered in a 3D crystalline structure. Atoms tend to pack together in the lowest energy states (most stable arrangements). Two ways of packing in silicates: First pack two layers on top of each other, then … 1) Cubic closest packing (CCP) = Third layer same position as first layer (atoms directly above atoms in first layer) This results in tetrahedral sites. 2) Hexagonal closest packing (HCP) = Atoms in the third layer in different position to first layer (atoms directly above spaces in the first layer). This results in octahedral sites. Big atoms fir into octahedral sites. Small atoms fit into tetrahedral sites.
What are the major mineral groups?
Explain Bowens reaction series.
What happens when you have molten rock (lava or magma) and then cool it?
The hotter the temperature when the rock forms, the more it will weather when exposed to the Earth’s elements.
