week 10 Flashcards
(22 cards)
stripping ratio
quantity waste removed/quantity of ore uncovered
stope
generic term for an underground mined volume or working to extract ore,
which is rock from which metal/mineral can be economically extracted.
Ore minerals
directly carry principal economic value, e.g., chalcopyrite, chalcocite
Gangue minerals
are unwanted constituents, e.g., silicates & carbonates in copper ore
Deleterious minerals/elements
impact negatively on value, e.g., arsenic in sulphides.
By-product minerals
carry minor saleable products, e.g., molybdenum, gold, silver
Run-Of-Mine (ROM) ore
ore flow from the mine
Development
generic workings mined for other (non-ore) purposes, e.g., access,
transport, ventilation. ‘Tunnel’ is used, but usually for relatively long distances.
Drifts, drives, crosscuts
Drifts - horizontal workings parallel to orebody strike.
Drives = similar, larger, longer,
generally for access. Cross-cuts = similar, perpendicular to strike.
Fill
Typically aggregates, sand and/or waste rock packed into exhausted stopes to fill
void and provide a floor for stopes above (Overhand Drift & Fill) or a roof for stopes
below (Underhand). Cement gives strength, esp. Underhand, but expensive or diluting.
Dilution
(percentage of) fill or waste rock (may have some grade) mixed into ROM.
Ore recovery
percentage of orebody mined as ROM
BC (block caving) Orebody
requirements:
- Large, ? > 50 Mt;
- Sub-vertical
orientation or
thickness; - Rock is weak enough
to cave and fragment; - Footprint large enough
for ‘Hydraulic Radius’
for caving to initiate; - Rock (+ rock bolts etc)
is strong enough to
develop complex
infrastructure below
cave volume; - Acceptable or
relatively high grades
at base of cave
volume.
drift and fill mining method
A variant of Cut & Fill, expensive,
but maximises orebody recovery & mining precision, i.e., ore – waste separation.
volume variance relationship
The larger the sample volume:
* The less random variation
(i.e., variance)
* The more representative it is
of the rock around it.
* But the more expensive it is
to drill/process/analyse/assay
* It’s a trade-off!
how are exploration results reported
Typically reported as drillhole intercepts
* E.g. 40m @ 2.5 g/t gold.
* “must not be presented so as to unreasonably
imply that potentially economic mineralization
has been discovered.”
* “inappropriate to use such information to derive
estimates of tonnage and grade or quality”
how are mineral resources reported
geological estimate – including sampling
* Must have “Reasonable Prospects for Eventual
Economic Extraction” (or RPEEE)
* Typically reported as tonnes & grades/q
* E.g. 32 Mt @ 2.23 g/t gold
how are mineral reserves reported
“Economically mineable … Mineral Resource”
* Subject to:
* Classification,
* Modifying Factors – including mine plan
* Dilution & losses
* “…studies demonstrate that … extraction could
reasonably be justified.”
surface mining
– low cost (if low stripping ratio) but high surface impact
– Open-Pit Mining
– drill-blast-load-haul-dump cycle
– Dredging
– Use of dozers and rippers.
Underground Mining Methods
– Low-cost methods (e.g., Block Caving) have high dilution & surface impact.
– High-cost methods (e.g., Cut & Fill) minimise dilution & surface impact.
mining geology activities
– Drilling, surveying, logging, sampling, analysis/assaying, QA/QC,
interpretation, estimation, mineralogy, and how to report mineral assets.
3 Processing Methods
-Gravity/Hydrodynamics – Froth Flotation – Leaching
– All requiring geological & mineralogical understanding to optimise.
