Mining Geology

Mining Geology

Introduction

What is mining? Mining is the process of excavating minerals of economic value from the earth’s crus for benefit of mankind. Here we can assume that the earth’s crust, the outer surface of the earth, including the oceans, lakes and rivers, extends to depths of 30 to 50 km or so. For mining operations, one should have a working knowledge of geology.

The word geology means the science of the earth and deals with the natural origin of the rocks that constitute the earth. A person interested in the extraction of minerals from the earth is, however, concerned with the thin surface of rocks that make up the earth crust to a depth of a maximum of 5 km so that geology enables him to locate, and to decide, the sites most economics form mining or quarrying.

In geology, the terms minerals and rock have precise but different meanings. A mineral is a homogeneous and naturally occurring substance having definite physical properties and a composition that may be expressed by a chemical formula. The chemical composition of a mineral as found in the earth, may be the same as that of an artificially prepared chemical compound in the laboratory but the physical characteristic may differ; e.g. lead sulphide, PbS, is generally available in the laboratory as an amorphous powder. It has quite different physical properties from galena, Pbs the name of the naturally occurring mineral, often in the crystalline form. Few minerals occur as single elements, e.g. native gold, silver graphite, but most minerals as single elements in chemical composition,, e.g. quartz (SiO2), hematite (Fe2O3) etc. Most rock-forming minerals are oxides, chlorides, sulphides, carbonates, sulphates or silicates. A rock may be composed of one mineral only but is usually a mechanical mixture or aggregate of two or more minerals. For example, granite is a rock composed essentially of three separate minerals; quartz, feldspar and mica. Whereas minerals can be considered as aggregates of chemical elements, so rocks are really aggregates of minerals. They contain minerals in varying proportions, and they have no definite chemical composition.

Bedrock is any rock lying in the position in which it was formed; it is therefore not broken up.

Country rock of an orebody is that rock that is predominant in the area and which contains the orebody. The country-rock forms the footwall and the hanging wall.

A seam is a mineral deposit limited by two, more or less parallel planes, a shape that is typical of sedimentary rocks. The term is generally used for coal, e.g. coal seam.

When excavating a useful mineral, the uneconomic rock or mineral associated with it which has to be excavated and discarded is called rejection, dirt or waste in coal mining practice and gangue in metal mining practice.

An ore is a rock that contains minerals and which can be used for economical extraction of metal after processing to separate mineral from the gangue. Ore usually occurs in veins or lodes.

If an ore when subjected to metallurgical processes, yields only one metal, it is called a straight ore.

A mineral deposit is a rock or mineral that is of economic value and repays its extraction from the earth.

A vein (or lode) shown in the figure below is a crack in the earth's crust filled with minerals. This filling can occur by precipitation of the mineral from the mineral-rich water or by the cooling of the magma filling the crack or by the separation of the mineral from vapours and gases rising up the crack. Vein, like seams, have a strike, a dip and a thickness but for the same vein, all these are usually quite variable.

vein or lode
vein or lode

A number of nearly parallel veins constitute compound lodes.

Orebody, the part of a vein that carries the ore. Generally, all parts of a vein are not ore.

Note that:

The country-rock contains the vein;

The vein contains the orebody;

The orebody contains the ore;

The ore contains the minerals;

The mineral contains the metal or metals.


keywords: 

mining geology, minerals and rocks definition in mining, the difference between rock and mineral, bedrock, seam, coal seam, country rock, vein, orebody, ore, mineral contains the metal or metals

Comments

Post a Comment

Popular posts from this blog

Different types of timber support

Image
Different types of timber supports  Timber props  Timber placed normally between the roof and floor of roadways, etc. in coal mines is called timber prop. Timber prop in metal mines is sometimes called stull. A timber prop when erected in a mine to support the roof should yield slightly under the roof weight. The timber prop is strongest when the load acts parallel to its length; a prop as such is almost unyielding but a certain yield is obtained by; a) tapering it at the foot or top, or b) and providing a lid at the top as a compressible cushion between the roof and the end of the prop. In flat seams the prop is erected vertical, and in inclined seams, axis of the prop should be normal to the dip of the seam. The prop then offers the maximum resistance to the roof. A prop which is so set that its axis is between the vertical and the normal to the seam is known as and underset prop. Erection of underset props is not common as it is not possible for the timberman to judge wh
Read more

Indicated , inferred, measured resources

Image
inferred  mineral resource  indicated mineral resource  measured mineral resource inferred mineral resource is that part of a mineral resource for which quantity and grade or quality can be estimated On the basis of geological evidence and limited sampling  An indicated mineral resource is that part of a mineral resource for which quantity, grade or quality, densities, shape and physical characteristics, can be estimated A measured mineral resource is that part of a mineral resource for which quantity, grade or quality, densities, shape and physical characteristics are so well established that they can be estimated estimated with a low level of confidence. It is inferred from geological evidence and assumed but not verified geological or grade  level of confidence sufficient to allow the appropriate application of technical and economic parameters, to support mine planning and evaluation of the economic viability of the deposit. with confidence suffi
Read more

Timber support for different places in mine

Image
Timber support in coal mine Side Support:  Wooden laggings are placed tight between vertical props and pillar where the sides are weak and need support. Sometimes the timber set of prop and bar has to resist pressure from sides which tend to crush into the roadways. Notching is useful in such cases. The props should be set at an angle of 14° to 20° off the vertical and the feet well sunk into the floor. An alternative method of resisting side pressure is to sink the props well into the floor and to reinforce the timber-set by an additional bar or stretcher (dotted bar in fig), which may be nailed to the props. As this reduces effective height of roadway, its use may not be advisable in roadways of less than 2 m height, used by basket loaders. Reinforced Timber set or chockmate Notched Prop Support of a Roadway:  Where the roof of a roadway is bad over some distance bars resting in holes of coal pillars and tightened against the roof by wooden laggings may be erected
Read more

50 common word roots, prefixes and suffixes

Image
50 Common Word Roots  prefixes and suffixes  for the GRE some words are made up of different parts, for example, unemployment. unemployment has a beginning (prefix), a middle (root word) and an ending (suffix) un-employ-ment            un ----->; prefix employ---->; root ment---->; suffix A root word is a real word and you can make new words from it by adding prefixes and suffixes. Root words are helpful for learning both the meaning and the spelling of a word.  here are sone more examples of root words and their woerd families: use:   use less,  use able,  use d, using,  use r, mis use friend:  friend ly,  friend ship, un friend ly ,  friend less faith:  faith ful,  faith fully, un faith ful, un faith fully Below find, a list of  50 common word roots, prefixes, and suffixes  that may help you on the GRE, as well as some words that use each of those roots. This list was drawn up by looking at what roots appeared repeatedly on official GRE
Read more

Options, Call & Put options, futures

Image
Option –  the right to buy or sell a futures contract at a particular price. The right to buy a futures contract is called a Call Option. The right to sell a futures contract is called a Put Option. The price chosen for which to buy or sell is called the Strike Price. The price paid for the right is called the Option Premium. Example of Call option order: Buy one contract November wheat call - €250 strike at €15 premium. Call Option  A contract which gives the purchaser the right, though not the obligation, to purchase the underlying security at a specific price within a specific time frame Suppose the Infosys is currently trading at INR 900. A trader thinks that the current price of Infosys is undervalued and expected to increase in the future. In this case, he buys the call option of Infosys and pays a premium to the call seller. Suppose the price of Infosys increases to INR 1000 at expiry. Then the buyer will exercise the option since he has the right to exercise. In this c
Read more

Unconformity-Related Uranium Deposit

Image
Unconformity-Related Uranium Deposits definition: Unconformity [ŭn′kən-fôr′mĭ-tē] A surface between successive strata representing a missing interval in the geologic record of time, produced either by an interruption in deposition or by the erosion of depositionally continuous strata followed by renewed deposition. An unconformity is a type of discontinuity.  or: An unconformity is time gap in the rock record between two rock units where the lower unit may be deformed, brecciated or altered and the overlying units are less deformed. Uranium deposits can occur in the underlying or overlying units. In the underlying units, there may be a weathering zone, fault zone or some other feature that increases the rocks porosity and permeability. In the overlying units, it may be the sandstones or some other features that allows the concentration of uranium.  Uranium unconformity deposits are generally associated with structures in sedimentary rocks that reflect the erosion surface
Read more

Sandstone uranium deposits

Image
 Sandstone uranium deposits Uranium deposits hosted in Sandstone, occur in medium to coarse-grained sandstones deposited in a continental fluvial or marginal marine sedimentary environment. Impermeable shale/mudstone units are interbedded in the sedimentary sequence and often occur immediately above and below the mineralized sandstone. Uranium precipitated under reducing conditions caused by a variety of reducing agents within the sandstone including: carbonaceous material (detrital plant debris, amorphous humate, marine algae), sulphides (pyrite, H2S), hydrocarbons (petroleum), and interbedded basic volcanics with abundant ferro-magnesian minerals (eg chlorite). There are five main sub-types of sandstone deposits, often mixed: Basal channel deposits – wide channels filled with permeable sediments. Examples are Dalur and Khiagda (Russia), and Beverley and Honeymoon (South Australia). Tabular deposits – irregular, elongate lenticular bodies parallel to the depositional trend,
Read more

Roof support in underground coal mine

Image
Roof support in underground coal mines Roof support in underground mines is used: To prevent major collapses of the mine roof; To protect miners from small rock falls that can occur from the immediate roof skin; To control deformations so that mine openings remain serviceable for both access and escape, as well as for ventilation of the mine workings Ensure continuity of ore production to avoid shortage in profit.  Finally, keeping expensive machines in the underground mines safe (e.g. machines used in long wall mining. When do we need to support mines? If there are weak or unconsolidated parts of rocks are present in the roof and walls of mines.  If there some geologic structures (e.g. shear zone) that weaken rocks.  If there are voids and spaces in the rocks. If there are some clay beds that can shrink and expand due to its swelling property, and hence sliding of rocks in presence of water can be expected. If there are underground water that helps in chemical wea
Read more