3.1 Introduction to Hard Rock Mining

Hard Rock Mining

• Hard rock deposits occur in sedimentary, igneous, and metamorphic rocks, unlike soft rock mining which typically involves coal.
• Hard rock mining involves exploring and mining an orebody, which is a mineral that can be exploited safely and at a profit.

Orebody Formation and Classification

• Orebody formation processes include weathering and erosion, volcanic processes, sedimentation, and tectonic or metamorphic processes.
• Weathering and erosion can break down rocks into minerals, which may become concentrated as either weathering-resistant minerals or in mobile minerals.
• Volcanic processes can result in concentrations through crystallization, differential gravity settling, and heat energy.
• Sedimentation can result in gravity separation and concentration within clastic sediments.
• Tectonic or metamorphic processes can result in the breakdown and transformation of rock minerals and concentration of certain elements.

Types of Orebody Formation

• Igneous intrusions include iron, ferro-alloy metals, non-ferrous base metals, precious metals, nuclear elements, magnesite, and barite.
• Sedimentary concentration by weathering and/or precipitation includes iron oxides, manganese oxides, bauxite, uranium, and vanadium.
• Sea water extraction includes salt and magnesium.
• Placer deposits include gold, cassiterite, mercury, zirconium, silica sand, rutile, ilmenite, and monazite.
• Pegmatite deposits include feldspar, quartz, rare earth minerals, lithium minerals, and beryllium.
• Evaporite deposits include potash, sodium carbonate, sodium sulphate, salt, borax, gypsum, and lithium.
• Chemically deposited sedimentary deposits include sulphur, phosphate, strontium minerals, barite, limestone, dolomite, magnesite, and chalk.
• Other sedimentary deposits include diatomite, clay, shale, sandstone, quartzite, bentonite, perlite, diamond-bearing rock, and graphite.
• Metamorphic deposits include mica, asbestos, talc, vermiculite, pyrophyllite, slate, sillimanites, and magnesite.

Indicators of Mineralization

• Rust-colored rocks or soil (Gossan) are a good indication of mineralization, caused by iron, which may indicate the presence of other metallic minerals.
• Quartz veins are often associated with sulphide mineral deposits.
• Dykes are long thin bodies of igneous rock that may contain or be associated with valuable minerals.
• Shear zones are places of weakness or breaks in the earth's crust through which mineralized solutions may have been channelled, and often contain quartz veins.