Glossary (A – E)

This page provides a glossary of geological terms to be found on the TVRIGS website and elsewhere. It is an evolving document and will grow as the site expands.

A

Adit
Mine entrance which extends either horizontally, or at a shallow angle, generally (though not exclusively) into a hillside. Adits may be used for drainage and/or as a travelling way for miners, ore, etc.
Alum
A double sulphate, either potassium or ammonium aluminium sulphate having the fomulae K Al (SO4)2 • 12 (H2O) and NH4 Al (SO4)2 • 12 (H2O) respectively. It is a (generally) white crystalline chemical, formerly manufactured in Cleveland and North Yorkshire using Alum Shale and employed in dying cloth, preparing (tawing) leather, paper and candle making, etc.
Alluvial
Pertaining to rivers. For example, alluvial deposits may describe the silts, sands and gravels laid down along the course of a river.
Amaltheid
A genus of index ammonites within the Lower Jurassic System occurring within the Upper Pliensbachian (Domerian) universal sub-stage.
Arenaceous Rocks
Detrital sedimentary rocks, typically sandstones but with varying amounts of other material, composed primarily of quartz grains with particle-sizes between 1/16mm and 2mm. Arenaceous rocks, from the Latin Arena meaning ‘sand’, can be further subdivided into ortho-quartzites and lithic-arenites with the former comprising c.95% quartz and the latter containing a lesser proportio of quartz and greater proportion of other minerals. For example, sandstone containing more than c.15% feldspars are known as arkose, coarse-grained sandstone is often dubbed Grit or Greywacke.

Argillaceous Rocks
Detrital sedimentary rocks composed of clay minerals with particle-sizes of less than 1/16mm. Argillaceous rocks, from the Latin Argilla – meaning ‘clay’, can be further subdivided into shales, mudstones, siltstones and marls. In addition to clay minerals argillaceous rocks may contain very finely-divided quartz, carbonate dust, carbon and/or pyrite.


B

Bed
May be either:

  1. The solid floor below a body of water (e.g. lake-bed, sea-bed, etc.)
  2. Identifiable rock unit of variable thickness within a succession.

Beds are generally, though not exclusively, delimited by the presence of bedding planes.

Bedding Plane
The surface of original deposition seperating beds.
Bedrock
Solid geology underlying a district. It may be exposed to the elements, or obscured by surficial deposits.
Berthierine
Formerly known as chamosite, berthierine is a complex iron silicate with chemical formula Fe2+1.5 Al Fe3+0.2 Mg0.2 Si1.1 Al0.9 O5 (OH)2. It constitues a major source of iron in the Cleveland ore along with the iron carbonate siderite (FeCo3).
Bord
A passageway excavated during mining operations. Bords are associated with pillars of unworked rock left to support the mine’s roof.

Cutaway of Bord & Pillar Working

Boulder Clay
Also known as diamict, till or drift. Boulder Clay is a generic term for a mass of clastic detritus (rock flour) and rocks of variable size primarily, though not exclusively, unstratified which is deposited during the wasting of an ice-sheet or glacier. Such debris is both accumulated and pulverised as ice advances, and may be transported for many hundreds of kilometers from its original outcrop. The fraction of non-local rocks contained in the diamict are termed erratics and are able to provide valuable information about the source and route of ice, many thousands of years after the ice itself has disappeared.


C

Calcine
Heating of quarried or mined material either:

  1. In kilns; or
  2. In the open air;

to assist in the breakdown of parent material and/or drive off volatile components.

In the case of ironstone, calcining involves heating rock to drive off water and unwanted volatile chemicals before the ore is placed into the furnace for smelting. The process, when employed with local ore, could increase the iron-content from c.33% to c.40%.

In the case of alum-making, Alum Shale is heaped into clamps and calcined to break down the rock and release aluminosilicates.

Nodules of calcium carbonate (CaCO3), known as cementstones and found just above the Main Alum Shales, were calcined before milling to produce hydraulic cement.

Calcium Carbonate
Mineral with the chemical formula CaCO3. It is the primary component of limestone and can often be found in nodular form within the Whitby Mudstone Formation.
Carboniferous
System of rocks named (by William Conybeare, 1822) from the widespread occurrence of carbon, in the form of coal, in these beds. It covers the episode in Earth’s history between c.360 million and 299 million years before present.
Cementstone
Calcium carbonate-rich rock, often nodular, suitable for cement making. Locally, the Whitby Mudstone Formation includes the Cement Shales which overlie the Main Alum Shales. These beds contained suitable nodules formerly extracted at Sandsend amongst other places.
Channel Sandstone
Sandstone deposited during the operation of a river channel. The deltaic beds of the Middle Jurassic locally contain numerous examples.
Cistern
Wood or stone-lined tank, often a pit, in which liquids (alum liquor, water, etc.) can be stored.
Clamp
A heap, or long ridge, of quarried or mined rock interleaved with combustible material (wood, coal, etc.). The clamp is burned in a controlled way which calcines the rock. During alum-making this part of the processing was carried out in the quarry.
Concentration
Phase in the processing of Alum Shale carried out in the alum-house. Following steeping of calcined shale, the resulting liquor is heated to drive off excess water by evaporation.


D

Desses
Narrow benches in the worked face of an alum quarry resulting from shale removal. The process of working rock in this way is known as dessing.
Dogger
A mining term used particularly in Yorkshire having more than one meaning. It can be either:

  1. A transitional formation marking the base of the Middle Jurassic in Cleveland and North Yorkshire.
  2. Nodules, either calcareous or sideritic.
  3. An impure form of ironstone, mainly sideritic, which may occur in the shales between ironstone beds.

Drift
The term drift has more than one geological meaning:

  1. Surface deposits of glacial origin; e.g. boulder clay (till), lake clays, silts, sand and gravel deposits. It derives from the early nineteenth century notion that such deposits, containing erratics were the result of deposition from ice which had floated (drifted) across open ocean before eventual deposition.

  2. A mine entrance extending more-or-less horizontally into a hillside, or at an angle into more level ground. See also Adit.

  3. Relative slow movement of continental plates making up Earth’s crust across the planet’s surface. Continental Drift, now termed plate tectonics was first mooted by Alfred Wegener (1880 – 1930).


E

Erosion
Wearing away of existing rocks and deposits by wind and/or water and/or abrasion.
Erratic
In geology, the term erratic refers to material moved by geologic forces from one location to another, usually by ice. The term is used to refer to rocks of non-local origin which can assist in determining glacial ice movement, often many thousands of years after the ice which formerly occupied an area has disappeared. See Wikipedia entry.


Glossary(F-K)»

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