When we think of the word ‘mining’, images of dark cramped corridors cut through the rock deep beneath the earth’s surface come to our mind. However, this is but one form of mining called ‘underground mining’.
“But isn’t all mining obviously done underground?”, you say.
No indeed! There are three other types of mining. Let’s discuss.
Firstly, where does the word ‘mine’ come from? It is Latin: mina, minera “ore”. And for those of you who don’t know, ‘ore’ is a naturally occurring solid material from which a metal or valuable mineral can be profitably extracted. [Source: Oxford]
4 Types of mines
In order to understand the types of different mines, the best way is to note the different materials collected by each mine. Essentially, the reason we have different types of mines is to mine different types of materials (metal, rock, sand), found at different depths in the Earth.
When desirable materials are near the earth’s surface, then we need a surface mine to extract them. In other words, there are no deep, dark chasms and drilling. Here are the different types of surface mines:
Open pit mines
These mines are unmistakable in their appearance. They cover a very wide amount of space (several kilometers), and they look like canyons or valleys, but with their slopes being ‘steps’, or ‘terraces’. Each step or terrace is actually a ‘road’, and the walls of each terrace level are blasted out, and put in a massive truck for processing. These types of mines typically mine ores like: copper, iron, aluminum. These mines employ blasting to remove the rock and get access to the ore.
These mines don’t go as deep as the open pit mines we mentioned above, and don’t look like canyons. According to the Citizens Coal Council “Explosives are used to fracture any overlying rock, and then heavy machinery is used to remove the overburden and dump it into a nearby area. Mining is done in long, narrow strips, thus the name ‘strip mining'”. Strip mines are most commonly used for mining coal.
At Kalamazoo, this is the type of mining we do. We perform a geological survey to find a mountain which is composed of the type of rock we want. We then very precisely blast off sections of the face of the mountain with explosives. Making sure that after the blast the mountain still retains its shape, otherwise too much material will collapse. As we blast off sections, we collect the rubble, and sort it into different sizes, and crush it further to get the exact sizes we need. Quarry mines are used for mining: sand, gravel, clay, granite.
Last and certainly not least, in fact the most expensive, we have underground mines! These are considerably more expensive to operate, therefore they are only used when the material being mined is highly valuable. In other words, you won’t see underground mines for extracting sand and gravel!
Why is mining important?
Mines provide minerals essential for today’s technology:
- Cars & trucks
The list goes on!
The quartz is needed for the screens for our mobile phones and laptops. Quartz comes from the mineral silicon.
The circuit boards and electronics we use need gold and silver.
Cars use steel. Steel is made from Iron, which comes from minerals magnetite and hematite.
Airplanes use aluminum (mined from bauxite) and platinum (mined from rutile and ilmenite).
In other words, if we couldn’t mine, we would not have the materials we need to make vehicles or electronics, not to mention the gravel and rock needed for building roads and making concrete for buildings.
We’ve got your gravel, sand and rock!
At Kalamazoo we have a wide selection of rock for your landscaping needs. Check out our catalogs, we’re confident we have the size and color that you need, no matter what type of project you have!
The most common way to get rock from the ground or mountains is by blasting and drilling. There are some locations where there are literal mounds of lose rock (that have formed naturally) but these are not as common, and when they do form there is not enough in quantity to supply all the area’s construction needs.
The process starts off with a geologic survey done to determine if the mountain is viable as a source for the desired type of rock (as not all mountains contain the same type of rock), and for how long (you want years and years of supply before committing to an operation as expensive as mining).
Track carriages mounted with drills will then be moved to the mountain’s face, where they will bore holes deep into the face of the mountain, however deep as necessary, from 15 feet and beyond. Holes are drilled 6-15 feet apart for small blast holes, and 30 feet apart for large blast holes.
These drill-mounted track carriages are ideal since they can freely move on jagged rock surfaces, from one drilling location to another, like a tank.
As the drill drills through, air is blown down into the hole. This keeps the drill bit cool and also allows debris to be blown out & removed. The rate at which the drill can drill through the rock can be from 20 to 100 feet per hour.
The most common explosives used in blast mining are dynamite and ANFO.
- Most sensitive, nitro-glycerin based and most expensive
- Most commonly used, liquid mix of ammonium nitrate, and number 2 diesel. It can only be detonated with special primers and is therefore safer.
Dynamite isn’t just thrown haphazardly and randomly at the mountain. There are several factors that must be taken into consideration.
One of them being the shape of the mountain. The blasting needs to be done so that: 1) the resulting rubble is accessible for collection 2) the remaining structure of the mountain is in a stable shape, 3) the next round of drilling and blasting will not be hindered
To achieve this, think of the mountain as a Thanksgiving Turkey. You’re shaving off pieces of meat from the outer-most part of the turkey, one thin slice at a time.
It’s similar with blast-mining. You approach the outer-most part of the mountain (the face), and that is the part that you blast off, and then keep working backwards from there, effectively carving off slices of the mountain.
To achieve this, sections are blasted off in carefully measured rows, so that each blast is an even slice off the mountain.
It’s vital that the explosions are controlled and planned in order to:
- Minimize flyrock (rock flying away and thus lost)
- Unwanted damage to the mountain
After the rock is blasted the rubble will be processed by crushing it and feeding it into various sized screens, collecting batches for each type of size, from large man-sized boulders to small 1inch gravel.
Why do companies do blast mining?
Put simply, it is the most inexpensive way to go about fracturing rock. Let’s face it, construction requires a lot of raw materials, and if the gravel had to be drilled by hand, the man-power needed would be unimaginable. By using explosives, the costs for rock are kept low.
Where should you get your rocks?
We have several quarries serving the NZ, AZ and CA regions. At Kalamazoo we’ve got what you need, and the most gorgeous colors in the area. Visit our catalog to see for yourself!