Unit 2 Refining Minerals

Question 1

physical process

Answer 1

using physical methods to extract minerals from ore or sediment

Question 2

alluvial

Answer 2

material deposited by a river

Question 3

sediment

Answer 3

small particles like sand, mud, stones or pebbles that have been deposited somewhere

Question 4

chemical process

Answer 4

the use of chemicals to extract minerals from ore

Question 5

refining

Answer 5

making a natural product pure by removing unwanted substances

Question 6

ning minerals

Answer 6

Most minerals are extracted from the Earth’s crust in the form of ore. While some minerals, such as diamonds, can be used in their natural form, other minerals require chemical or physical processes to extract the minerals from the ore.

Question 7

Physical methods of extraction

Answer 7

Gold found in alluvial deposits is extracted by physical processes. These methods were used mainly in the early days of gold discoveries when the gold was easy to find and separate. Gold sluicing and panning are two such methods that are still used today. Sluicing involves shovelling river sand and gravel into a sluice box, the dense material is washed down the sluice and the fine gold particles stay behind. Panning involves taking sand and gold dust from a sluice box, or sometimes gravel directly from a river alluvial sediment, into a wash basin or pan and swirling it around. The gold drops to the bottom. The gold dust and flakes can then be collected from the bottom of the pan.

Question 8

Riffle tray with expanded metal sheets

Answer 8

Ribbed matting for quick inspection

Question 9

Flared flat sluice

Answer 9

Figure 6 A gold sluice

Question 10

Chemical methods of extraction

Answer 10

Many minerals are mined through chemical methods of extraction. Chemical processes often involve dissolving the ore using a suitable chemical, and then removing the mineral from the chemical solution. Heat and oxygen can also be used to remove impurities from minerals (refining).

Question 11

banded iron stone

Answer 11

The rock in Figure 8 is called banded iron stone. It was an important source of iron ore for some of the first iron-using people in South Africa. They devised a chemical process using charcoal, oxygen from the air and intense heat to extract the iron.

Question 12

Chemical methods of extraction

Answer 12

Many minerals are mined through chemical methods of extraction. Chemical processes often involve dissolving the ore using a suitable chemical, and then removing the mineral from the chemical solution. Heat and oxygen can also be used to remove impurities from minerals (refining).

Question 13

banded iron stone

Answer 13

The rock in Figure 8 is called banded iron stone. It was an important source of iron ore for some of the first iron-using people in South Africa. They devised a chemical process using charcoal, oxygen from the air and intense heat to extract the iron.

Question 14

archaeologist

Answer 14

a scientist who studies ancient people

Question 15

smelting

Answer 15

to process an ore using heat to extract the mineral that is in the ore

Question 16

steel

Answer 16

a mixture (alloy) of iron and other materials, mainly carbon

Question 17

alloy

Answer 17

a mixture of different metals to produce a new type of metal with better qualities than any of the components in the alloy

Question 18

coke

Answer 18

is a fuel made from coal in the same way that charcoal is made from wood. So you can think of it as ‘coal charcoal. It is high in carbon

Question 19

Safety

Answer 19

Lead oxide is a toxic (poisonous) substance. Do not touch it with your hands, taste it or breathe in any fumes given off in the experiment.

Question 20

Investigate how lead is extracted from its ore

Answer 20

Activity 4 You will need: • lead oxide • charcoal powder • teaspoon • good quality test tube • test tube holder • thin rod • safety goggles - heat proof surface • Bunsen burner or other gas flame 1. Put half a teaspoon each of lead oxide and charcoal powder into the test tube 2. Mix the mixture well with a thin rod. 3. Hold the test tube using a test tube holder and heat the mixture strongly for five minutes. (Move the test tube back and forth over the flame to ensure even heating.) 4. Allow the mixture to cool down. 5. Tip out the mixture onto a heat-proof surface. 6. Examine the mixture closely. 7. What do you find? What do you think the new substance is? Activity 4 uses a chemical method to produce lead metal. When you heated lead oxide with charcoal powder (actually carbon) the oxygen combined with the carbon and made carbon dioxide gas. The gas went into the air. What was left behind was metallic lead, plus various impurities and some of the original powder that did not fully react. This is how lead is extracted from lead ore.

Question 21

Traditional knowledge of iron and copper extraction

Answer 21

People have known how to extract metals like iron and copper from ore for thousands of years. For example, iron ore was heated with charcoal to make lumps of iron. There is lots of evidence that has been collected by archaeologists from across South Africa, particularly from archaeological sites in KwaZulu-Natal and Limpopo. Smelting iron ore using furnaces was first carried out in South Africa about 1700 years ago in parts of Limpopo. There is evidence that these people then moved southward and eastward into KwaZulu-Natal. Iron-working people settled at Broederstroom near Hartbeespoort Dam about 1 150 years ago and at Melville Koppies in Johannesburg about 800 years ago. Mapungubwe in the northern Kruger National Park was settled by a group of iron workers about 1 000 years ago. it did not take long for iron smelting skills to spread through most of South Africa. Smelting is the process whereby heat is used to extract a mineral from its ore. People chose sites that had trees to make charcoal from, iron ore in the rocks, water nearby and grazing for their cattle.

Question 22

iron smelting

Answer 22

When early iron smelting people needed to get iron to make implements like hoes, spears or cutting blades they used a special furnace like the one shown in Figure 9. Their furnaces had a small chimney and side openings for blow pipes. (These did exactly the same job as the ones you used for the lead oxide activity - they increased the flow of oxygen and increased the temperature of the flames.) Layers of charcoal and crushed iron ore in the ratio 1 to 10 were laid inside the furnace and this was set alight. The fire was lit in the late afternoon on a full moon night. This was for visibility and also for ritual reasons.

Question 23

bellows

Answer 23

Two assistants worked the goatskin bellows to pump air into the furnace to raise the temperature. A team of smelters would work through the night. Each smelter had two bellows, which he would pump at up to 120 beats per minute. After a whole night, a small lump of iron might be produced.

Question 24

steel

Answer 24

Steel is an alloy (a mixture) of iron and carbon. Steel is iron that has had most of the impurities removed. The properties of steel are superior to iron on its own. Steel is stronger, harder and lighter than iron.

Question 25

blast furnace

Answer 25

To extract the iron a blast furnace is loaded with iron ore, coke (a form of coal) and small quantities of other materials to assist the process. It is called a blast furnace because air is blasted into it during the smelting. Air that has been heated to about 1 200 °C is blown into the furnace.

Question 26

coke

Answer 26

Coke is very high in carbon, like the charcoal in the Iron Age smelting furnaces. The coke burns and reacts chemically with the iron ore to release the iron from it. This iron has about 4 to 5% carbon in it which makes it brittle and not useful for very much.