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Metal mineral resources
Formation of mineral deposits
1 Magmatic deposits
2 Hydrothermal deposits
3 Seafloor massive sulphide deposits
4 Secondary enrichment deposits
5 Sedimentary deposits
6 Placer ore
Ore exploration and mining
Specification material
Crushed stone and concrete
In January 1848, James Marshall and a group of workers were discovering gold
in gravel scattered on the bed of a nearby stream in the foothills of the Nevada Mountains.
That year, the gold rush swept the country, and by 1849 40,000 explorers had come to California
.
Gold is just one of many metal mineral resources, which refers to the earth's resources
that contain metals such as gold, copper, aluminum or iron.
Metal is an opaque, shiny, smooth solid that conducts electricity and can be bent, pulled into metal wires, or beaten into sheets
.
The first metals that people learned to use (copper, silver, and gold) were those that existed in rocks in the form of natural metals
.
A natural metal is made up of only metal atoms, so it looks and behaves like metal
.
For example, natural gold in gold nuggets looks like processed gold
in a bracelet.
While prehistoric people could find some readily available metals to make weapons, coins, and jewelry, modern societies had many other sources of metal
.
Most of the metal atoms we use today were originally ions
bound to non-metallic elements in minerals.
Natural gold
2 What is oreGeologists use the term "ore" to refer to rocks
that contain special metals worth mining.
The concentration of useful metals in the ore determines the grade of the ore, and the higher the concentration, the higher the
grade.
In ore, metals can come in the form of natural metals or in the form of specific minerals, which are called ore minerals
.
For example, galena (PbS) contains 50% Pb, so we consider it a Pb ore mineral
.
Hematite (Fe2O3) and magnetite (Fe3O4) are iron-bearing ore minerals, Cu is derived from a variety of ore minerals, including chalcopyrite (CuFeS2), porphyry (Cu5FeS4), and malachite [Cu2CO3(OH)2].
As you can see from the chemical formula of these examples, many ore minerals are sulfides (metals bound to S); or oxide (metal bound to O).
Galena (PbS) crystals grown in dolomite; Copper-bearing ore minerals composed of azurite (blue) and malachite (green).
Formation of mineral deposits
Ore minerals do not occur uniformly in the earth's crust, and geological processes concentrate ore minerals in areas rich in large amounts of ore, the so-called ore deposits
.
Geologists distinguish between different types of deposits based on the process by which they formed:
1 Magmatic deposits
In some magma, ore minerals crystallize early and accumulate to form ore lenses, called magma deposits
3.2 Hydrothermal deposits
Hydrothermal fluids intrude through igneous rock, and as they circulate in the surrounding rock, they dissolve metal ions
.
When the resulting hydrothermal solution enters different environments (lower pressure, lower temperature, different acidity, or different oxygen content), the metal precipitates into ore minerals, forming hydrothermal deposits
.
When ore minerals precipitate in cracks, they form vein-like ores, and when they precipitate in pores, they are dispersed throughout the rock, and they form impregnated ores
When the ore mineral crystallizes, magma deposits can be formed in the magma chamber; Hydrothermal deposits are formed when hydrothermal fluids carry dissolved metals away and precipitate
3.3 Seafloor massive sulphide deposits
Along the mid-ocean ridge, hydrothermal vents called black smokestacks eject hydrothermal fluid, which is mixed with seawater and cooled, and the dissolved components precipitate into sulfides distributed along the vents
Massive sulphides on the seafloor are distributed along vents
3.4 Secondary enrichment deposits
In the upper part of the earth's crust, groundwater dissolves ore minerals and carries away ions
through ore.
When water flows into another environment, it precipitates new ore minerals, forming secondary enriched deposits
5 Sedimentary deposits
Sedimentary deposits are deposits formed by the settlement or precipitation of ore minerals from water as sediments, built with banded iron
Constructed with strip iron
3.6 Placer ore
When rocks containing natural metals are eroded, the resulting sediments contain rock fragments and metal flakes or lumps (pebble-sized fragments).
Moving water carries away lighter particles, but heavier metal particles cannot be easily moved, so metal particles concentrate in the gravel to form placer deposits
Ore exploration and mining
Past explorers rode tired donkeys in the wilderness in search of outcrops of milky quartz veins that may contain natural metals, or spots of color caused by oxidation (rusting) of ore minerals
.
Gold prospectors stirred gravel in plates filled with water, washing away lighter mineral particles, leaving behind heavier ones, which may include gold
.
When a possible deposit is found, the prospector will bring the sample back to the city for testing, and if the test results show a high concentration of metal, the prospector may mark a piece of land with a stake to "establish ownership
".
Today, commercial mining companies employ geologists to investigate potential mineral-bearing areas
.
Geologists help identify promising sites by measuring the strength of local gravitational or magnetic fields, as minerals tend to be denser and more magnetic than the average rock
.
They can also sample rocks, soil and plants to test metal concentrations
.
If surface observations indicate ore underneath, geologists drill samples and analyze the rock
beneath the surface.
Subsurface data may eventually help determine the shape and size
of deposits.
The three-dimensional shape of underground deposits, mines and tunnels allows miners to enter the deposits
To develop an open-pit mine, workers drilled a series of holes in the bedrock and detonated explosives in precise sequences so that the rock would break into stones of the right size for easy handling
.
The front-end loader unloads the rock onto a huge ore truck, which dumps the waste rock into a tailings pile and then loads the ore into a crusher to crush the ore into small pieces
.
The ore fragments are sent to processing plants, where workers use various methods to separate the ore minerals from other minerals
.
Finally, ore mineral concentrates are smelted, separating their metal atoms from
those of other elements.
Surface mining refers to the mining of ore fairly close to the surface, and steps chiseled into the wall help ensure the stability of the wall
To mine deposits 100 meters below the surface, miners built an underground mine
.
Either dig a tunnel on the side of the mountain, or dig a shaft
.
Where deposits appear in the earth's crust, they build a labyrinth of tunnels
in the ore by drilling holes in the rock and then blasting.
Removed rocks must be returned to the ground
.
The rock pillars between the tunnels support the ceiling
of the mine.
An underground mine hewn into a mountainside in Colorado
6Mining and the environmentSome of the large basins caused by open-pit mining are so large that astronauts can see them
from space.
Both open-pit and underground mining produce huge tailings piles
.
Due to the lack of soil cover, tailings piles may not grow vegetation for decades
.
In some places, mining companies soak tailings with acidic solutions to filter metals, which can destroy vegetation if these acids leak into the environment
.
Mining metal ores, just like mining coal, exposes minerals to air and water
.
These minerals may dissolve to produce acid ore runoff that kills vegetation
downstream.
Similarly, fumes from ore smelting can contain harmful chemicals such as sulfur, which dissolve in water to produce acid rain that can wreak havoc
on the surrounding countryside.
New technologies and regulations and efforts to encourage recycling have reduced the environmental damage caused by metal mining and processing, but our demand for metals continues to grow, so it is likely that environmental issues related to the mining and use of metals will continue to pose challenges
for future generations.
Environmental impact of producing metal resources
7How long can metal resources last?Most metal mineral resources are non-renewable and once mined, the deposits disappear forever
.
Under the current definition of reserves, the supply of some metals could run out
in decades to centuries.
In addition, metal mineral reserves are not evenly distributed across the planet, and not all countries have equal access to mineral supplies
.
This issue is very important from a national security point of view, and some minerals (strategic minerals) are essential
for high-tech devices such as computers and batteries.
Efforts to enhance conservation and recycling can significantly reduce consumption rates, thereby extending the life
of existing reserves.
Recovery rates may increase
when the cost of recycling is lower than the cost of extracting new minerals.
Consider the materials you can see in a typical house or apartment: concrete, brick, glass, wall panels
.
Society uses many such non-metallic mineral resources, earth resources other than metals, where do they come from?
Specification material
Dimension stone, which is more durable
than almost all other building materials.
We use stone for facades, roofs, curbs, steps, countertops and floors
.
The names given to various types of stones by architects, designers, or contractors may differ from
the official rock names used by geologists.
For example, architects refer to any polished carbonate rock as "marble," whether metamorphosed or not, and any crystalline rock containing feldspar or quartz as "granite," regardless of whether the rock has an igneous or metamorphic structure, or a felsic or mafic component
.
To obtain intact slabs or stones from the quarry, workers can split the stones from the bedrock by hammering a series of wedges, creating the spread of cracks, or they can use a variety of power tools to cut the cracks from the bedrock walls
.
Examples of such tools include cable saws, heat spray guns, water jets
.
Once workers remove the gauge from the quarry, the gauge can be cut into smaller pieces
.
Stone production in quarries
2.Crushed stone and concrete
Gravel is the basis of roads and railways, as well as the raw material
for cement, concrete and asphalt.
At the crushed rock quarry, operators use explosives to break the bedrock into crushed stone, which is then trucked to the crusher
.
The crusher processes the crushed stone into usable dimensions
.
Large gravel quarries
Many buildings built in the last century use concrete
.
To make concrete, workers mix cement with aggregate (sand and/or gravel) and water to create a slurry
.
When discussing concrete, cement refers to a powder that contains various chemicals and is soluble in water
.
When workers pour wet concrete into a mold, it hardens into a solid, producing a complex assemblage
of artificial mineral crystals.
These crystals hold together particles of aggregates, just as crystals precipitated from groundwater bind together sand grains in sandstone
.
The cement in concrete is mainly composed
of lime (CaO), a small amount of silica (SiO2), alumina (Al2O3) and iron oxide (Fe2O3).
In the 18th and early 19th centuries, workers only needed to put a special type of limestone block into a kiln to produce cement, which contained small amounts of quartz and clay
in addition to calcite.
When heated to 1450°C, calcite (CaCO3) decomposes in limestone to form lime (CaO) and carbon dioxide gas (CO2), clay and quartz provide other oxides
in cement.
The special limestone needed to make this "natural cement" is quite rare, so Portland cement
is used for most concrete production today.
Workers heat limestone, sandstone and shale in the right proportions to provide the chemicals
needed to make cement.
The long pipe is a rotating kiln in which the rock injected at one end is heated to high temperatures and cement flows out from the other
Although the earth is rich in non-metallic mineral resources, their use comes at a cost
.
At present, the transportation of non-metallic resources accounts for a large part of its costs, so supply companies try to locate quarries as close to consumers as possible
.
In the future, at least in some places, other land uses may compete with quarrying and limit the availability of
these resources.
Source: Taocheng News
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.
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.
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