The Aggregates & Recycling Information Network

Glossary: O

  • OBM

    abbr. ordnance bench mark.

  • Obsidian

    Volcanic glass of granitic composition, generally black with vitreous lustre and conchoidal fracture.

  • OCCS

    abbr. opencast coal site

  • Occupational Exposure Standard

    The concentration of airborne substance at which level it is not likely to be injurious to health.

    abbr. OES

  • OD

    abbr. ordnance datum

    The land-levelling datum, being the mean sea level determined at Newlyn, Cornwall, the use of which makes comparison of the heights of installations throughout the UK possible. 

  • OES

    abbr. occupational exposure standard

    The concentration of airborne substance at which level it is not likely to be injurious to health.

  • Offset

    A horizontal distance measured at right-angles to a survey line to locate a point adjacent to it.

  • Ohm

    The resistance between two points of a conductor when a constant difference of potential of one volt, applied between these two points, produces in this conductor a current of one ampere.

    Symbol: ?

  • Old Red Sandstone

    General term for sandstone of the Devonian period.

  • Olivine

    Magnesium iron silicate, (MgFe)2SiO4, occurring in basic igneous rocks, eg olivine-basalts; typically dark olive-green to brown in colour.

  • Onyx

    Ornamental banded variety of cryptocrystalline silica.

  • Oolite

    Sedimentary rock, characterised by small spherical grains of calcium carbonate.

  • Oolith

    Small, usually spherical, grain built up of calcium carbonate.

  • Ooliths

    Ellipsoidal or spherical accretionary bodies, usually less than 1mm in diameter, composed of concentric layers of calcite, aragonite or iron carbonate.

  • Open Circuit
    1. A flow line in which the solid particles pass from one appliance to the next with no fraction being returned for retreatment.
    2. The state of an electrical circuit when there is a break in continuity.
  • Opencast

    Open cut, mineral deposit worked from surface, open to daylight.

  • Operator

    The person (or company) in overall control of the working of a quarry.

  • Ordinary Prescribed Mixes

    Concrete mixes for which the proportions of aggregate, cement and water have to be in accordance with the quantities specified in BS 5328:1981.

  • Ordinary Shareholders

    The owners of the business. These shareholders participate in the distribution of the profit remaining after payment of the preferential shareholders. This dividend is declared as a percentage of the par, or nominal value of the shares.

  • Ordnance Datum

    The land-levelling datum, being the mean sea level determined at Newlyn, Cornwall, the use of which makes comparison of the heights of installations throughout the UK possible.

    abbr. OD 

  • Ordovician

    A period of the Palaeozoic era, ranging from 505 to 435 million years ago.

  • Ore

    Solid mineral of actual or potential economic interest.

  • Orogeny

    Period when rocks are severely folded, metamorphosed and uplifted, as opposed to longer periods when activity is less; igneous activity is greater in orogenic periods.

  • Orthoclase

    Potassium aluminium silicate (KAlSi3O5) a member of the feldspar family. Important as a constituent of acid igneous rocks. Used in the manufacture of glass, pottery etc.

  • OS

    abbr. Ordnance Survey.

  • OSS

    abbr. open-side setting. see ‘setting’. It regulates the size of the largest particle released from a crusher.

  • Outcrop

    The area where part of a rock stratum, or any other deposit, appears at the surface, any cover of soil being ignored.

  • Overburden

    Material, whether consolidated or not, which has to be removed before a mineral can be worked.

  • Overburden Ratio

    The ratio of the vertical thickness of the overburden to the thickness of the mineral to be mined in a stratified deposit.

  • Overcurrent Protection

    Protection of a system against excessive electrical currents.

  • Overflow

    That proportion of the feed discharged from the screen without having passed through the apertures.

  • Overhead

    The costs not directly associated with a unit of production which are apportioned over a range of operations or products; the indirect costs.

  • Overload

    In electrical or mechanical engineering, a load greater than that for which the plant is designed.

  • Oversize

    Material in a product of a size greater than the upper nominal size; may be expressed as a percentage of the product.

  • Owner

    The owner of a quarry within the meaning of section 181 of the Mines and Quarries Act 1954.

  • Oxidizer

    An ingredient in an explosive or blasting agent which supplies oxygen to combine with fuel to form gaseous or solid products of detonation. Ammonium nitrate is the most common oxidizer used in commercial explosives.