Chapter 4: Minerals

Question 1

Define a mineral (3)

Answer 1

• Naturally formed chemical substance having a definite (not fixed) composition and characteristic crystal structure
• Cannot be broken into different mineral substances
• Often present imperfections in form, colour, and and properties

Question 2

Define a mineraloid. (2)

Answer 2

• Amorphous naturally occurring substance

- Lacks arrangement of iron and atoms

Question 3

Describe colour (3)

Answer 3

• One of the trickiest properties
• Can be significantly affected by impurities
• Example: malachite and azurite

Question 4

List the five common descriptive terms of lustre and give an example of each. (5)

Answer 4

1. Vitreous (glassy), quartz
2. Metallic, galena
3. Dull, hematite
4. Silky, gypsum
5. Greasy, halite

Question 5

What are the four ways crystals are formed? (4)

Answer 5

1. Molten matter crystallization (most common)
2. Liquids with high ion content solidify
3. Biological activities (bacteria)
4. High temperatures, pressure, and chemically active fluid regimes

Question 6

What are the three type of crystal faces and forms? (3)

Answer 6

1. Euhedral: fully developed with angular/acute corners
2. Subhedral: elongated, prismatic form, rounded corners
3. Anhedral: irregular as a result of less space

Question 7

Describe twinning (2)

Answer 7

• Symmetrical intergrowth of two or more crystals of the same substance
• Examples: Staurolite (cross), calcite (twist)

Question 8

Give examples of the native elements that are metals (4), semimetals (3), non-metals (2)

Answer 8

Metals: Gold (Au), Silver (Ag), Platinum (Pt), Copper (Cu)
Semi: Arsenic (As), Antimony (Sb), Bismuth (Bi)
Non: Carbon (C), Sulphur (S)

Question 9

Define sulfides and sulfosalts.

Answer 9

Sulphides are formed with a metallic element and sulfur, often metallic but not all are

Sulfosalts are a combination of a semi-metallic element with metallic

Question 10

What metals make up these sulfides:

• Galena
• Cinnabarite
• Chalcopyrite
• Stibinite
• Realgar and orpiment

Answer 10

Galena: Lead (Pb)
Cinnabarite: Mercury (Hg)
Chalcopyrite: Copper (Cu), Iron (Fe)
Stibinite: Antimony (Sb)
Realgar and orpiment: Arsenic (As)

Question 11

Define carbonates (4)

Answer 11

• Contains CO3 (Carbonate)
• Well developed and rhombohedral
• Commonly bright
• Most common is Calcite

Question 12

Describe sulfates. (3)

Answer 12

• Combined with SO4 (sulfate)
• Most common is gypsum
• Soft, light and present in pale colours

Question 13

What are the silicate mineral groups? (6)

Answer 13

Isolated (neosilicates)
Single (inosilicates)
Double (sorosilicates)
Sheet (phyllosilicates)
Ring (cyclosilicates)
Framework (tectosilicates)

Question 14

Describe neosilicates and provide three examples (3,3)

Answer 14

• Do not have direct bonds (electrons) between
• Linked by cations (triangles and circles)
• Most frequent silicates
• Examples: Olivine (most frequent on surface), topaz, zircon

Question 15

Define inosilicates

Answer 15

Single chains, ionic bond by other metals (wave)

Question 16

Define sorosilicates (2)

Answer 16

• Two or three shared oxygens

- Double chains bonded by cations ( stars + 4 green dots)

Question 17

Describe the two mica minerals. (2)

Answer 17

White mica: occurs in acidic and continental crust
Black mica (biotite): in oceanic crust

Question 18

Define phyllosilicates

Answer 18

• Three shared oxygen atoms (honeycomb)

Question 19

Define tectosilicates (3)

Answer 19

• All bonded with covalent bonds
• 3D framework
• Appears more homogenous