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Glossary of Geological and Mining terms

 

A   B   C   D   E   F   G   H   I   J   K   L   M  N   O   P   Q   R   S   T   U   V   W   X   Y   Z

 


 

A
 

ADIT 
A nearly horizontal underground opening having one end in daylight.  Adits have widely been used as prospecting excavations, for example those at Coltonpits, and for mine drainage.

 

ANTICLINE 

A fold, either symmetrical or asymmetrical, in which the limbs slope upward. 

 

AXIAL PLANE
( of a fold).  An imaginary plane that divides a fold, longitudinally, into two parts which may be, but are rarely mirror images, one of the other.

 

B

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BACK 
The roof of a stope or other mine working.  (Also the outcrop of a lode, though this term is rarely used today).

BEDDING 
Sedimentary rocks, including those of which the Brendon Hills are made, are usually laid down in layers, one on top of the other, which differ to a more or less well marked degree in composition, grain size, colour or some other property.  Such layers are called beds or strata.  The separation planes between beds are bedding planes, and the whole set of beds shows stratification.  A group of beds is called a formation.

BUCKET LIFT PUMP 
The lowest pump in the mine sump.  It was so designed as to be relatively easy to move downwards as the shaft was deepened.  At its foot, submerged in water, was an egg-ended perforated cast iron cylinder with a non-return valve at the top.  Attached to the pump rod above was a cylindrical iron barrel inside which was a piston rod with a bucket  fixed to its lower end.  As the pump rod was raised by the beam engine, the piston rod was raised, the non-return valve opened and water was drawn into the chamber above; when the piston descended on the next stroke the flap valve closed and water was forced up the cylinder to discharge into the cistern of the lowest plunger pump (qv).

 

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CAPEL 
A layer or vein of barren quartz of variable thickness, frequently found accompanying Brendon Hills iron ore lenses, where it forms the footwall.

CARBONIFEROUS 
Pertaining to the second-oldest system of the Upper Palaeozoic Era.  The Carboniferous succeeded the Devonian.

CELLULAR ORE
= “POTTY” ORE (a  Brendon Hills term).  Secondary oxide iron ore having cavities or openings in it, the cavities being due to volume changes brought about by alteration of primary carbonate, spathic ore to secondary oxides.


CLEAVAGE 
Argillaceous rocks, such as the Brendon Hills Beds, contain a high preponderance of clay or fine silt.  Under the influence of high stress caused by deep burial, folding and earth movement, a natural slatey grain or cleavage develops in these rocks such that they become thinly laminated.  Orientation of the cleavage or lamination is parallel or sub-parallel with the axial planes of cleavage folds such as the Brendon Syncline and Anticline, also with the dip of iron ore lenses.  In the Brendon Hills, cleavage dip (= lode dip), varies from about fifty degrees to nearly vertical depending on location.

 

COLLAR 
The opening at surface of a shaft.

 

COMPOUND SHAFT
(such as Raleighs Cross old engine shaft), have abrupt changes in azimuth (direction), as well as inclination.

 

COUNTRY ROCK 
Those barren rocks lying above, below or surrounding an orebody.

 

CROSSCUT 
A nearly horizontal underground opening driven from a shaft or as an adit, to intersect a steep, tabular mineral deposit in the shortest possible distance, which usually is at right angles to the direction of the crosscut.  (eg. Gupworthy level was a crosscut adit, as was the Kennisham Hill adit and Poorsland adit at Eisen Hill mines).

 

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DEADS 
Waste: barren rock waste.

 

DEVONIAN 
Pertaining to the oldest system of the Upper Palaeozoic Era.  The term includes the continental Old Red Sandstone as well as the Marine Devonian. A deltaic facies intermediate between these two rock types includes the Brendon Hills Beds; consisting of siltstones, slates and fine grained sandstones;  the Beds are probably a shallow water, marine facies, though an absence of fossil remains within them fails to prove this probability.

 

DIP 
The angle that a bedding plane or other surface such as cleavage, on, or in a rock makes with the horizontal.  True dip of a bedding or cleavage plane is measured at 90 degrees to its strike.  Apparent dip is the angle as measured in any other direction, and will always be a value less than the true dip.

 

DRIFT 
a shaft (qv) - a coal mining term applied, by way of the Welsh connection to many Brendon Hills shafts.

 

DRIVE
( = level, end or roadway ). A development ‘tunnel’, usually originating from a shaft, having a slight inclination which may be as little as 1% away from the shaft, excavated in or parallel with, an orebody.  The term ‘level may be synonymous with ‘drive’ or it may refer to all underground workings situated at a particular horizon or elevation in an underground mine.  The term ‘roadway’ more usually refers to levels either in a coal mine, or other stratified deposit, such as gypsum or salt.  The term ‘end’ implies an uncompleted level or drive: that is, having a rock face at the inbye end.

 

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FACIES 
The general aspect of a group of strata  is spoken of concisely as its ‘facies’. The term may have reference to either rock characteristics, or fossil contents.

 

FAULT 
A fracture plane or zone of fracturing in the earth’s crust.  The rocks on either side of the fracture plane or zone are usually displaced on one side of the fault plane relative to the other.  Relative movement may be from vertical to horizontal, or any combination of the two.  The horizontal element of apparent relative displacement may be right- or left-handed.  The former is known as dextral, and the latter, sinistral.  (The Timberscombe Fault Zone has a sinistral element of horizontal displacement, since the relative movement of rocks on either side of it is to the left).

 

FOLD 
A bend in a rock mass, such as a bend in a series of strata.

 

FOLD AXIS 
(directional: of a cleavage, or other, fold).  An imaginary line that passes through the points where the axial plane of a cleavage fold cuts a cleavage or bedding plane surface.

 

FOOTWALL 
The lower contact between a lode and barren rock lying beneath.

 

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GANGUE MINERALS 
The associated non-metallic minerals of a deposit: they may be introduced minerals, even the enclosing rock, and are frequently of only nuisance value: ( such as the quartz capel in the Brendon Hills mines).

 

GUNNIS 
A large, man-made cavity, usually produced by the removal of ore from a stope.  In the Brendon Hills mines these were frequently unstable (eg. at Eisen Hill mine), and liable to collapse, unlike the open gunnises in Cornish mines which were between hard, competent, granite walls.

 

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HANGING WALL 
The upper contact between a lode, and barren, overlying rock.

 

HORIZON 
A horizontal plane of specified depth below surface, upon which certain geological features of a mine are evident.  It is also a term used in mine surveying where accuracy of depth needs to be known.  (A series of glass plates one beneath the other at uniformly spaced intervals, with the mine geology of each horizon marked and painted on the plate, are often accumulated in the mine geologist’s or surveyor’s office.  Such an accumulating collection of plates, one below the other, renders the geology of the mine instantly readable in three dimensions.)

 

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INBYE 
Innermost.  Generally a coal mining term, but a descriptive one.

 

K

 

KILLAS 
(a west of England term). (1). Thermally and pressure-altered sedimentary or other rock surrounding an igneous intrusion.  (2)  A fine grained sedimentary rock containing a high proportion of clay minerals and silt, the whole having cleavage imposed upon it due to intense pressure, such that it assumes a shaley or slatey characteristic (facies).

 

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LAGGING 
strong timber lining to maintain a ‘raise’ in being.

 

LEVEL 
Sometimes loosely used in place of the more definitive ‘horizon’ (qv): thus one may refer to the ‘10 fathom level’ or to the ‘60 fathom level’.  That these roadways may rise and fall somewhat, above and below the named level is of no great consequence.  The actual name is used for identification purposes only, and is an approximation.

 

LITHIFICATION 
The conversion of soft sediment to hard rock by ageing, and processes of deep burial, raised pressure and sometimes appreciably raised temperature. The end product is said to be LITHIFIED.

 

LODE 
A sheet-like structure consisting of mineralization, economic in width and depth for mining.  The term ‘vein’ may sometimes substitute for ‘lode’, though it also applies to sheet-like structures of gangue minerals of no commercial value, (on the Brendon Hills, the quartz ‘capel’).   Lodes may be lenticular in shape - that is, discontinuous in depth and lateral extent.  They may sometimes then be said to form ‘pods’ or ‘lenses’ of ore.  Gangue = worthless material, but beware the application of that term, for today what may appear to have no commercial value may, tomorrow be highly prized.

 

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MESOZOIC 
Pertaining to the second of three great geological eras, lowest being the Palaeozoic, and highest being the Cenozoic, formerly known as the Tertiary.

 

METAMORPHIC ROCKS 
Rocks altered by heat or pressure or both: ‘changed’ rocks.

 

MINERALS 
A mineral is a substance having a definite chemical composition and atomic structure and formed by the inorganic processes of nature.  According to this definition, coal and oil are not minerals, though in a commercial sense, they are.

 

MORPHOLOGY 
Shape.  ( eg. of landforms, fossils, iron ore lenses etc.).

 

O

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ORE  
The term is often loosely used to designate anything that is mined.  Technically, it is an aggregation of ore minerals and gangue from which one or more metals may be extracted at a profit.

 

ORE LENS 
An orebody of roughly double convex shape in both horizontal and vertical directions.

 

ORE MINERALS 
An ore mineral is one that from which one or more metals may be obtained.

 

ORE PASS 
A vertical or sub-vertical connection between stoping levels and/or sub-levels of a mine.  Such passes are for the transfer of ore only.

 

OVERHAND (STOPES) 
Also overhead.  Some stopes produce ore by mining from level to level in an upward or overhead direction; these are known as ‘overhand stopes’.  They have the great advantage that ore broken in them migrates downwards, assisted by gravity, to loading points.  The converse of this is ‘underhand’, where the stope is worked in a descending, labour-intensive sequence of operations.

 

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PERMO-TRIASSIC 
Pertaining to the top of the Upper Palaeozoic Era and the base of the succeeding Mesozoic Era.  Climatically, the arid conditions of sediment deposition in both Permian and Triassic eras were sufficiently similar for the two to be lumped together and referred to as the Permo-Triassic or New Red Sandstone era.  The two eras’ life forms however, were significantly different.

 

PILLAR 
(No plural in the mining sense).  Unbroken underground rock or ore left in situ to protect/support backs or walls in or near stopes, shafts etc.

 

PLUNGE 
If the axis of a fold is not horizontal, as is the case of the Brendon Anticline/Syncline cleavage folds, it is said to plunge.  The amount of plunge is the angle between the fold axis and the horizontal, as measured in the vertical plane

 

PLUNGER POLE PUMP 
A pump at any level in the mine except the sump.  The plunger was fixed to the lower end of a timber plunger pole which was strapped to the side of the main pump rod.  As the pump rods were raised by the pumping engine, so too was the plunger, and its motion produced suction which lifted the lower of two non-return valves and drew water into the pipe.  On the engine’s next stroke the pump rods descended and the lower non-return valve was forced shut.  At the same time the upper valve was forced open pushing a column of water into the rising main and so up to the surface. 

 

PRIMARY ORE MINERALS 
Those deposited during the original period or periods of metallisation: (the carbonate ores of the Brendon Hills = spathic ore, siderite or ‘white’ iron ore of the formula FeCO3, containing, on average,12% of manganese).

 

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RAISE 
(noun) A shaft, vertical or inclined with both its collar and bottom underground, which has been excavated from the bottom upward.  A ‘raise’ is usually constructed for underground ventilation purposes, or to serve as an ore pass down which ore is transferred to a central shaft-loading point whence it is hoisted to surface through the mine’s main shaft.  (verb) The act of excavating a shaft from the bottom upwards.

 

RAKE 
(of Brendon Hills ore lenses = ‘end slant’) the approximate angle of inclination of both east and west ends of ore lenses towards the west: the complement of ‘plunge’.

 

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SECONDARY ORE MINERALS 
Alteration products of primary minerals. (In the Brendon Hills context refers to primary spathic ore changed by oxidation, mainly weathering, to the secondary iron oxide mineral, haematite, and the hydrated oxides limonite and goethite; also occasionally, from the 12% manganese content of spathic ore where sufficiently concentrated, to the manganese hydrated oxide mineral, psilomelane.

 

SHAFT 
A vertical or inclined opening serving underground mine workings.  Inclined shafts are usually sunk with uniform gradient (for high speed hoisting), in barren rock close to the mineral deposit which they serve.  Vertical shafts are sunk in barren rock, and do not usually intersect the mineral deposit they serve, unless the latter is sub-horizontal, (eg. A coal seam).   See also: ‘compound shaft  drift and ‘underlay shaft

 

SHAFT COLLAR 
The uppermost part of the shaft where it emerges to daylight.  It is where the uppermost shaft timbers, known as the collar set, are laid, from which all others in descending sequence are suspended by means of bolts and adjustable threaded hooks to provide a sequence of perfectly horizontal sets.

 

SHAFT WINGS 
A hinged stout timber platform raised and lowered by chain and pulley, having curved tram rails are fixed to its upper surface.  The wing was fixed in place at each tramming station to enable the transfer of mine trams from haulage level to the steep, variably inclined shaft.  The curved rails had to be (1) incrementally curved upwards from the nearly horizontal plane of the tramming level to that of the inclination of the rails in the shaft, and 2) curved through as much as 90 degrees horizontally turn turn the tram from the haulage level orientation to that of the shaft rails.  Thus each of the two rails attached to the wing was in the form of a matching half corkscrew, the rails tapering vertically each end, no mean achievement when the sole means of doing so was a Jim Crow or pinch bar operated rail bending device.  When the wings were in the lowered position, mine trams were pushed as far as possible into the shaft to allow them to be coupled to the winding rope.  When in the raised position, the wing allowed full or empty wagons to pass through unhindered to or from other levels above or below.

 

 
(of the Brendon Hills mines).  A front loading railcar not unlike a coal scuttle on four wheels, used for hoisting ore in skip shafts.  The skip, unlike a tram, never leaves the shaft but is filled at a subsurface loading station, and automatically tipped at surface into an ore bin before being immediately let down the shaft again for refilling.  In modern vertical and inclined shafts, skips may operate in tandem.  In the Brendon Hills underlay shafts, they did not.

 

SKIP SHAFT 
A shaft devoted to the skip hoisting of ore to surface.  Trams would not be hoisted through a skip shaft.

 

STOPE 
That underground mine working in a mineral deposit which, with correct development and preparation, yields profitably worked high tonnages of mineral in the shortest possible period of time.  A stope is the space between the hanging - and foot - wall from which ore is removed.

 

STOPING 
The rapid profitable removal of an underground mineral deposit by mining.  The profitable stoping of a mineral deposit may be regarded as the sole purpose of mining.

 

STRATIGRAPHIC OR STRATIGRAPHICAL 
The order in which sediments have been deposited, always with the oldest at the base and the youngest above. The Stratigraphical Column shows the order in which Geological Systems occurred and their relative duration.

 

STRIKE 
The direction in which a horizontal line can be drawn on a bedding plane or other structural surface, such as cleavage, at any particular point.  Strike is always at 90 degrees to true dip.

 

STULL 
A length of undressed timber, often a stout coniferous round pole straight from woodland or forest, used underground for wall support or some constructional purpose such as the erection of chutes for ore transfer.

 

SUB-AERIAL 
Rocks formed not as most are, under the ocean or sea water, but either on dry land or in shallow, brackish waters such as characterise deltas or swamps.

 

SYNCLINE 
A fold, either symmetrical or asymmetrical, in which the limbs slope downward.  A symmetrical fold is one in which the limbs on either side of the axial plane are mirror images. (The Brendon Syncline is asymmetrical).

TAKE  An antiquated term formerly used in lieu of ‘lease’, and one sometimes favoured by some Victorian solicitors averse to the word ‘lease’.

 

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TRAM 
A deep side-, or end-tipping waggon, usually having four wheels, used to transfer ore, waste, materials etc. in and out of the mine.  Brendon Hills mine trams may have carried loads of about one-and-a-half or two tons of ore or waste.  Flatbed trams are used to carry long timber pieces or stulls from the shaft to the working place.

 

U

 

UNDERLAY SHAFTS 
Shafts sunk on the dip of the lode, and thus irregular in their inclination.

 

W

 

WINDING 
(verb): applied to the raising of ore trams, skips etc. to surface.

 

WINZE 
Frequently an underground prospecting shaft with its collar underground.  Excavated from the top downward.  Until the introduction of mechanisation, winzing was very hard and demanding work, as all rock broken by blasting had, of necessity, to be hand-loaded into a kibble (bucket) or tram if the winze was inclined, from a rough floor and hoisted to the level above.

 

 

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