Chapter 3a Silicate Minerals (Chemical Classifications & Examples)

Question 1

What are the most COMMON ELEMENTS in the Earth’s Crust?

Answer 1

Silicon & Oxygen

Question 2

What is the most COMMON MINERAL GROUP?

Answer 2

Silicates (90% of the earth’s crust)

Silicon and Oxygen elements combined to form Silicates (a mineral group)

Question 3

What is the structure of silicon-oxygen tetrahedra?

Answer 3

-has a molecular formula of (SiO4)4- with a negative 4 charge
-consists of 4 oxygen surrounding a smaller silicon atom
-forms a negative ion

Question 4

How are the groups of tetrahedra held together?

Answer 4

-the groups of tetrahedra are held together by positively charged ions (cations) such as Fe Mg K Na Ca

Question 5

What are the arrangements of tetrahedra?

Answer 5

1. Independently - Olivine
2. Long chains - Amphiboles & Pyroxenes
3. Sheets - Mica
4. 3D - Quartz & Feldspar

Question 6

How are the conditions and the environment during which the cooling occurs determine the TYPE OF SILICATE formed?

Answer 6

1. Quartz
   - formed near the surface of the Earth where the temperature & pressure is low
   - composed of Si and O
2. Olivine
   - formed deeper in the earth where the temperature & pressure is higher
   - composed of Mg and Fe

Question 7

What is the most COMMON SILICATE Mineral? Why?

Answer 7

1. Feldspar
   -the most common silicate mineral in earth’s crust
   -making up more than half of Earth’s crust
   -distinguished by their 3D arrangements of tetrahedra
   -they are named for the cation presents: K-feldspar contains potassium
2. Quartz
   -the second most abundant silicate mineral in earth’s crust
   -the only common mineral made completely of Si and O
   -3D arrangement of tetrahedra
   -lacks of cation

Question 8

What are the other silicates?

Answer 8

1. Micas (such as muscovites)
   -sheets tetrahedra arrangement
   -can be cleaved into sheets of material, as the bond holding e groups of tetrahedra are not as strong as Si-O tetrahedra
2. Amphiboles (such as hornblende)
   - long chains tetrahedra arrangement
   -found in granite
3. Olivine
   - independent tetrahedra arrangement