Mineral Properties and Bonding and Mineral Classes

Question 1

Define the major groups within the carbonate class

Answer 1

• Anhydrous carbonates: Calcite group (e.g., calcite, magnesite) and Aragonite group (e.g., aragonite, cerussite).
• Anhydrous carbonates with compound formulas: Dolomite group (e.g., ankerite, dolomite).
• Carbonates with hydroxyl or halogen: (e.g., malachite, azurite).
• Hydrated carbonates: (e.g., lansfordite).

Question 2

definition of carbonate

Answer 2

Carbonates are a class of minerals with the basic anionic unit consisting of a triangle with a carbon, nitrogen, or boron atom at the center.

Question 3

Difference between Calcite, Dolomite, and Aragonite:

Answer 3

• Calcite is the most common carbonate mineral, with a trigonal-hexagonal crystal structure. It is used in cement and lime production.
• Aragonite is another polymorphic form of CaCO3, occurring in orthorhombic crystals. It is typically acicular in shape.
• Dolomite has a similar composition to calcite but differs in crystal structure. It contains alternating layers of calcium and magnesium, resulting in distinct cleavage and acid reaction differences.

Question 4

Describe the major groups of native elements,
sulphides, oxides and hyroxides, their properties and use

Answer 4

• Native Elements: Only 20 elements occur naturally in their elemental state, such as gold, silver, copper, and sulfur.
• Sulphides: Sulphide minerals contain the S2- anion and are important ores of various metals, including pyrite, pyrrhotite, and chalcopyrite.
• Oxides: Oxides include minerals like hematite, rutile, and magnetite, often exhibiting dark colors and symmetry in their crystal structures.
• Hydroxides: Hydroxides share properties with oxides and commonly include iron hydroxides like goethite formed through weathering of iron minerals.

Question 5

Use Moh’s hardness scale and appreciate its importance in identifying minerals.

Answer 5

The Mohs hardness scale is a scale from 1 to 10 that measures the relative hardness of minerals. It is based on the ability of a mineral to scratch another mineral. The scale helps in identifying minerals because harder minerals can scratch softer minerals, but not vice versa.

Question 6

List the four kinds of bonds, and how they relate to hardness and other physical properties.

Answer 6

The four kinds of bonds are covalent, ionic, metallic, and van der Waals.
Covalent bonds are the strongest + sharing of electrons
ionic - ions joined in crystal structure (strong) + one ion has pos charge other has neg (cation and anion)
metallic bonds - weak bond + electron is free to drift through the structure
van der waals bond - weakest bonds + ‘forces’ tie neutral molecules into lattice + not often found in minerals (micas, clays)

Question 7

Define the terms cleavage and fracture.

Answer 7

• Cleavage is the tendency of minerals to break along specific planes of weakness due to differences in bond strength. It results in smooth, flat surfaces.
• Fracture is the way a mineral breaks when it does not follow cleavage planes. Fracture surfaces can be irregular and lack atomic order.