Lab 2

Question 1

What are minerals

Answer 1

Minerals are the basic building blocks of rocks, they are defined as a chemical element or compound that is a naturally occurring crystalline solid and is formed as a result of inorganic processes.

Question 2

What are the 3 defining characteristics of minerals

Answer 2

1. a mineral is homogeneous throughout
2. A mineral has an ordered three-dimensional crystalline lattice. This gives the mineral its properties
3. A mineral has a limited and definite chemical composition.

Question 3

How do rocks differ from minerals

Answer 3

Rocks can be composed of a mixture of different minerals, pieces of organic material and fragments of other rocks. They do not have a crystalline nature, though the minerals within them do. And they can have a wide range of compositions based on component minerals.

Question 4

how many minerals are there

Answer 4

There are over 3000 minerals discovered, but less than 30 make up the bulk of earth’s crust. These are called the rock-forming minerals

Question 5

How are minerals classified

Answer 5

Minerals are classified based on the anion in their crystalline structures.
Groups of chemically related minerals are called classes. Many characteristics of minerals within a class have similar physical properties

Question 6

What are the most common types of minerals

Answer 6

Silicates make up ~1/3 of all mineral types. They make up around 95% of earth’s crust.

Question 7

What are Native element minerals

Answer 7

Minerals with no anions consisting of one element only. Ex: Sulphur, Graphite, Diamond, Gold

Question 8

What are Sulphides

Answer 8

Minerals with Sulphur as the anion, ex: Pyrite, galena, Sphalerite, Pyrrhotite.

Question 9

What are Oxides/hydroxides

Answer 9

Minerals with the anion of oxygen or hydroxyl.
ex: hematite, corundum, magnetite, bauxite

Question 10

What are Halides

Answer 10

minerals with an Anion of fluorine or chlorine. Ex: Fluorite, halite, sylvite

Question 11

What are Carbonates

Answer 11

Minerals with carbonate (CO3 2-) as the anion.
Ex: dolomite, calcite, siderite

Question 12

What are Sulphates

Answer 12

minerals with sulphate (SO4 2-) as the anion. Ex: Gypsum, anhydrite, barite

Question 13

What are Phosphates

Answer 13

Minerals with phosphate (PO4 3-) as the anion. Ex: apatite

Question 14

What are Silicates

Answer 14

Minerals with the anion being Silicon-oxygen tetrahedral (SiO4 4-) in different linkages.
Ex (Phyllosilicate): mica, talc, chlorite, clay minerals
Ex (others): quartz, olivine, pyroxene, amphibole, feldspars.

Question 15

what are a mineral’s diagnostic properties

Answer 15

the few characteristic physical properties that are most distinct and useful for accurate identification.

Question 16

What are the most important properties

Answer 16

basic lustre, hardness, and cleavage. And some that are only applied to certain minerals such as streak, magnetism, acid reaction, detailed nonmetallic lustre, fracture and colour.

Question 17

what are the steps for identifying minerals

Answer 17

1. Determine the minerals basic lustre (metallic vs non metallic)
2. Determine the minerals hardness range
3. Look for cleavage planes and determine how many there are and the angle at which they intersect
4. Make observations of other properties that may be of use:
   - Streak is useful with metallic minerals but rarely with non metallic
   - Colour is the easiest thing to observe, but most minerals occur in a variety of colour so its not always useful
   - The detailed lustre of nonmetallic minerals can sometimes be distinctive
   - only a couple metallic minerals are magnetic and a couple nonmetallic minerals react to acid
   - Exact specific gravity is not quick to determine, however it is worth noting if the mineral seems unusually heavy or light for its size.
5. Finally use these observations to navigate the mineral identification tables which will allow to reach a final identification

Question 18

What is Lustre

Answer 18

the amount and quality of light reflected from the mineral surface. Basic lustre can be initially indentified as metallic or nonmetallic

Question 19

What is metallic lustre

Answer 19

a mineral that reflects light in a way similar to metal. can vary in reflectivity from bright and shiny like aluminium foil to dull like old coins.

Question 20

What is non-metallic lustre

Answer 20

Minerals that do not resemble metal and are further subdivided into different light reflective categories such as glassy, pearly, earthy, and waxy.

Question 21

What is hardness

Answer 21

a measure of the resistance of the specimen to abrasion or scratching and is determined by both mineral composition and its atomic structure

Question 22

how do you test hardness

Answer 22

by measuring its scratchability with reference to minerals of known hardness. These test minerals are arranged in a standard hardness scale known as Moh’s scale of hardness.

Question 23

what is Moh’s scale of hardness

Answer 23

a list of minerals from 1-10 in order of increasing hardness. Each mineral scratches minerals below but not above it.

Question 24

What are the 10 minerals on Moh’s hardness scale

Answer 24

1. Talc
2. Gypsum
   2.5 finger nail
3. Calcite
   3.5 copper penny
4. Fluorite
5. Apatite
   5.5 Glass plate and metal scratcher/knife
6. Feldspar
   6.5 streak plate
7. Quartz
8. Topaz
9. Corundum
10. Diamonds

Question 25

How do you test hardness

Answer 25

1. Find the cleanest part of the specific and find a smooth surface on which to test. Press a sharp corner of the testing material against the specifimen and attempt to make a small scratch 2. check to see if you've made a scratch by cleaning the sample of any powder. Use hand lense 3. reverse the procedure and test the test material. If they scratch each other they have similar hardness

Question 26

How should you test with glass or a scratch plate

Answer 26

hold it flat on the table, and draw the specimen firmly across it

Question 27

What should you do when testing hardness with a mineral of small granular crystals (aggregates)

Answer 27

Aggregate will break apart easily. Use hand lens to determine just what scratching has done

Question 28

Is hardness always the same for the same minerals

Answer 28

no, ex Hematite ranges from 1-6 depending on how well crystallized it is

Question 29

How should you test hardness on a mineral with obvious cleavage

Answer 29

Perform the hardness on all cleavage planes, sometime one is harder than others

Question 30

what is cleavage

Answer 30

the tendency of the mineral to break along well-defined planes which represent planes of weakness in the lattice.

Question 31

What is the outer crystal face

Answer 31

represents the planes of growth of the minerals. Which is not always the same as cleavage. Quartz has a flat outer surface, but no cleavage planes

Question 32

what is fracture

Answer 32

how a mineral breaks along non-cleavage plane. Most have an uneven fracture. However a few has more distinct fracture such as conchoidal where it is smooth and curved (mostly for glassy minerals)

Question 33

What are some cleavage characteristic of common minerals

Answer 33

Quartz, garnet, and olivine have no cleavage Graphite, muscovite, biotite, and talc has one plane Pyroxene and feldspars have two at 90º Hornblende has two not at 90º Galene and halite have three at 90º Calcite and dolomite has three not at 90º (rhombic cleavage) fluorite has four planes Sphalerite has more than four (12)

Question 35

what are some hints for determining cleavage

Answer 35

1. Look for flat shiny surfaces on mineral specific, not number of directions of those surfaces 2. Determine the approximate angle between cleavage planes 3. If you're having difficulty, check mineral tables to see what type of cleavage your mineral should have.

Question 36

what is colour

Answer 36

Colour of a mineral results from absorption of certain wavelengths of light by the mineral. Many minerals occur in multiple colours, so colour isn't the most useful. Many minerals also display the same colour. Metallic minerals and native elements often has distinguishable colour.

Question 37

How can reaction with acid help with mineral ID

Answer 37

Carbonate minerals can be distinguished from other minerals by the fact they react with acids. Note: go easy on acid, a small drop will do

Question 38

How does magnetism help ID minerals

Answer 38

a few metallic minerals (magnetite and pyrrhotite) are strongly attracted by magnet

Question 39

What is Odor

Answer 39

Kaolinite a clay mineral is the constituent of earth or soils which gives the earthy smell when moistened. Sphalerite gives a rotten egg smell when dilute HCl is on it

Question 40

What is feel

Answer 40

some minerals have a greasy or soapy feel either due to basal cleavage (graphite, talc) or to dissolution of minerals by moisture on hand (halite)

Question 41

What is streak

Answer 41

streak refers to colour of the mineral when a portion of it is crushed along a porcelain streak plate. Most minerals leave the same streak regardless of their colour. Non metallic minerals give a white or very pale streak.