mining Flashcards
In mining, what is the cut-off grade?
the grade at which the gross value of the mined ore
is equal to the cost of mining
In mining, what is cost?
Cost = cutoff grade x price x recovery
What affects whether mineral resources can become reserves or ores?
Mineral resources can become reserves or ores and vice versa depending on technological advances and market price.
Legal, environmental and economic constraints must be considered for a resource to become a reserve.
What % wt in the Earth’s crust are abundant metals?
greater than 0.1% wt
What % wt in the Earth’s crust are scarce metals?
less than 0.1% wt
These are more difficult to find and therefore more expensive to extract
Metals can be classified as abundant or scarce. How are the scarce metals further classified?
Ferro-Alloy metals (Nickel, Chromium) Base metals (Copper, Lead, Zinc, Tin) Precious metals (Gold, Silver, Platinum) Special metals (Gallium, Rare Earths, Lithium)
Why is pyrite not mined for iron?
Because there are severe environmental issues associated with it
why aren’t all minerals in which the abundant metals (e.g. iron, aluminium) are present considered ore minerals?
not all minerals are able to be economically extracted
e.g. aluminium is present in many silicate minerals but extraction is prohibitively expensive
most ore minerals of the abundant metals are simple oxides, hydroxides or carbonates
From prospecting, to metal production what are the stages in project development?
1) Prospecting and exploration (Find potential mineral resource)
2) Resource estimation (how big is it?)
3) Feasibility studies (is it worth mining?)
4) Mine development (how is it going to be mined?)
5) Processing (what else do we need to do to produce the final product?)
All factors must be considered to determine whether a project will proceed
Most copper ore minerals are what?
Sulphides:
Chalcopyrite (CuFeS2)
Bornite (Cu5FeS4)
Chalcocite (Cu2S)
What is Recovery?
The fraction of the metal in the feed to the process that is recovered to the concentrate stream
Recovery = Flowrate of metal in concentrate/flowrate of metal in feed
What is grade?
The mass fraction of metal in the feed, concentrate or tailings
Grade = mass in stream/total mass of solids in stream
What factors affect grade and recovery?
Particle size (huge production costs) Mineral liberation Operating parameters (chemicals used etc) Feed grade Tonnage
What is a smelter or NSR (Net Smelter Return)?
A smelter will pay for metal but charge for treatment; this sets desired grade of the final concentrate from the separation
A simple smelter contract might be:
Revenue = mass metal x price - mass concentrate x treatment charge
How are oxide minerals produced?
Oxide minerals are a result of weathering of a sulphide ore
In an ore body, what is found beneath the oxidised zone?
There is sometimes a very high-grade sulphide ore zone of secondary enrichment beneath the oxidised zone and therefore beneath the water table
What are the primary Cu sulphide deposits?
Magmatic segregation deposits
Hydrothermal deposits
Sediment-hosted stratiform deposits
What make up the Hydrothermal Cu deposits?
Small veins - most have been exhausted because they were easy to mine (e.g. Cornwall)
Porphyry copper deposits -major source of copper ore (60%)
Skarns - associated with porphyry-type ores (e.g Antamina)
Volcanogenic massive sulphide (12%) (e.g. black smokers)
*remainder as bi-product of Ni and Pb-Zn ores and reprocessing of dumps
What are the main characteristics of porphyry copper deposits?
tend to be very large, contain small fractures
low grade but profitable due to size
What make up Sediment-hosted stratiform deposits and what percentage of Cu comes from these types of deposits?
Marine sedimentary rocks (shales)
20%*
*remainder as bi-product of Ni and Pb-Zn ores and reprocessing of dumps
What stages are involved in the methodology of Prospecting and Exploration?
Before mining can occur, a strategy consisting of the following steps is carried out:
- Target Generation
- Target Identification
- Target definition
- Evaluation (pre-feasibility/feasibility)
- Target Generation during Prospecting and Exploration consists of what strategic decisions?
Do we have the right to the land holdings?
What risks are there (political, climate etc.)?
What are the mineral types and their associated challenges?
- Target Identification during Prospecting and Exploration is done how?
Using key exploration techniques such as:
Geology: interpretation of mineral environments origins and variations
Geochemistry: Detection of mineralization in vegetation, soil, sediments and rocks
Remote sensing: Satellite/airborne analysis of earth data
Geophysics: Detection of mineral deposits physical properties