Lecture: Minerals
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What is a mineral?
Basic building block of rocks forming naturally in the Earth with a unique composition and structure
What is the criteria to classify a material as a mineral?
Naturally occurring - formed by geological processes, not synthetic Inorganic - not derived from the tissue of living things Orderly crystalline structure - atoms arranged in a repetitive, orderly pattern Solid state Definite chemical composition- has a specific chemical formula
What is a rock?
A naturally occurring solid aggregate of minerals or mineraloids
What are mineraloids?
Organic material
How are rocks classified?
Composition - what minerals are present Texture - grain/crystal size, shape and arrangement Formation process- how the rock formed Structure - large-scale features
What are optical properties of minerals?
Luster Color Streak Diaphaneity (light transmission)
What is luster?
How light reflects from a minerals’s surface metallic, submetallic, nonmetallic
What is streak?
The color of a mineral’s powder. Obtained by rubbing the specimen across the surface of an unglazed porcelain tile
What is diaphaneity?
The ability of a thin slice of mineral to transmit light Transparent, translucent, opaque
What is habit?
The typical shape of a mineral’s crystals
How is habit determined?
Primarily controlled by a mineral’s atomic structure Also growth conditions such as temperature, pressure, space and impurities can modify the final habit leading to variations even within the same mineral
What are mineral strength properties?
Hardness Cleavage Fracture Tenacity
What is hardness?
A mineral’s resistance to scratching
What is cleavage?
A mineral’s tendency to break along flat, parallel surfaces due to weak atomic bonds
What is fracture?
The way a mineral break when it does not cleave along flat planes Occurs when atomic bonds are equally strong in all directions, preventing cleavage
What is tenacity?
A mineral’s resistance to breaking, bending or deformation when subjected to stress
What is density?
How heavy something feels for it size
What is specific density?
A mineral’s weight compared to the weight of an equal volume of water
What are mineral groups?
A classification of minerals based on similar chemical composition and internal structure
What are the silicates?
A mineral group divided into two groups based on their chemical composition and physical properties Felsic vs Mafic
What is the silicate structure?
All silicate minerals contain silicon and oxygen The silicon-oxygen tetrahedron is the fundamental building block of all silicate minerals The structure consists of one silicon ion (Si) covalently bonded to four oxygen ions, forming a pyramid-like shape to make SiO4 4- It can link in different ways to form a variety of silicate mineral structures that differ in properties
What mineral group is most abundant in Earth’s crust?
Silicates
What elements are most abundant in Earth’s crust?
Oxygen and Silicon
What is felsic?
Silicate minerals that are light in color, less dense Contain aluminum, potassium, calcium, and sodium