Rabbit Lake – Uranium mill site owned and operated by Canada’s Cameco Corporation. Production began in 1975 and since then five or more orebodies have been mined to produce over 180 million pounds of U3O8 at the site.

Radar – System whereby short electromagnetic waves are transmitted and any energy which is scattered back by reflecting objects is detected.

Radial Drainage – System of streams running in a radial pattern away from the center of a circular elevation such as a volcano or dome.

Radiative Transfer – Mechanism for the movement of heat in which it takes the form of long-wavelength infrared radiation.

Radioactivity – Energy emitted as particles or rays during the decay of an unstable isotope to a stable isotope.

Radio-Carbon Dating – Scientific method used for determining the age of an organic substance by measuring the amount of the carbon isotope, carbon-14, remaining in the substance; very useful for determining ages in the range of 500 to 70,000 years.

Radiolarian – Class of one-celled marine animals with siliceous skeletons that have existed in the ocean throughout the Phanerozoic Eon.

Radiolarian Ooze – Siliceous deep-sea sediment composed largely of the skeletons of radiolarian.

Radiolarite – Lithified sedimentary rock formed from radiolarian ooze.

Raised Beach – Ancient beach that is located above the present shoreline; it indicates that the sea level has fallen and/or land has risen over time.

Ray – Linear landform of the lunar surface emanating from a large crater and extending as much as 100 kilometers outward, probably consisting of fine ejecta thrown out by the impact of a meteorite.

RC Drilling – Reverse circulation or rotary drilling method that uses a double-walled drill pipe. Compressed air and water is forced down the space between the two pipes to the drill bit and the drilled chips are flushed back up to the surface through the centre tube of the drill casing.

RCRA – Resource Conservation and Recovery Act was passed by the US Congress in 1976 to regulate solid and hazardous waste being disposed of.

Reaction Series – Series of chemical reactions occurring in a cooling magma by which a mineral formed at high temperature becomes unstable in the melt and reacts to form another mineral.

Rebound – Uplifting of a land mass after a weight has been removed.

Receiver – Part of an acquisition system that senses an information signal.

Recharge – Replenishment of ground-water in hydrology by infiltration of meteoric water through the soil.

Reclamation – Restoration of a site after mining or exploration activity is complete.

Recovery – Proportion of valuable material, in process metallurgy that is obtained in the processing of an ore. It is generally stated as a percentage of valuable metal in the ore that is recovered compared to the total valuable metal present in the ore.

Recovery Rate – Percentage or proportion of valuable metal in the ore that is recovered by metallurgical treatment.

Recrystallization – Growth of new mineral grains in a rock at the expense of old grains.

Rectangular Drainage – System of streams in which each straight segment of each stream takes one of two characteristic perpendicular directions, with right-angle bends between.

Recumbent Fold – Overturned fold with both limbs nearly horizontal.

Red Bed – Sedimentary layers composed primarily of sandstone, siltstone, and shale that are predominantly red in color due to the presence of iron oxides.

Reef – Large ridge or mound-like structure within a body of water that is built by calcareous organisms such as corals, red algae, and bivalves. A prime example would be Australia’s Great Barrier Reef which is a reef growing offshore from a land mass and separated by water.

Reference Model – Best-guess scenario, built up from limited a priori information about the composition of the earth in the region of interest that is used as a starting point.

Refining – Final stage of metal production in which impurities are removed from the molten metal.

Reflection Coefficient – Ratio of the reflected to incident amplitudes of a pulse reflected from an interface in seismic reflection and GPR.

Refraction (Wave) – Departure of a wave from its original direction of travel at the interface with a material of different index of refraction (light) or seismic wave velocity.

Regional Metamorphism – Metamorphism occurring over a wide area and caused by deep burial and high internal temperatures of the earth.

Regional Signal – In geophysical exploration methods, in particular gravity and magnetic methods, we are most often looking for spatially narrow anomalies that might be the signature of subsurface deposits or related structures. In many such cases the signal from larger scale, “regional,” sources might obscure that of the exploration targets we are interested in locating. As such, it is often prudent, and indeed necessary, to estimate the part of the signal from regional sources in order to subtract this from the observed data to yield residual data that better reflects the anomalies produced by spatially limited exploration targets.

Regolith – Solid material lying on top of bedrock. Includes soil, alluvium, and rock fragments weathered from the bedrock.

Regression – Drop in sea level that causes an area of the earth to be uncovered by seawater terminating marine deposition.

Regularization – Data are finite number of inaccurate observations, therefore there are many more model parameters than data and we don’t want to produce a model that will exactly reproduce all the data. As a result the data don’t uniquely constrain all of the model parameters and there are an infinite number of models that, when forward modeled, will reproduce the data to within the specified standard deviations. This inherent instability is regularized through the introduction of a model objective function which enables us to choose the type of model recovered. In this function a priori information can be applied in the form of constraints. In the absence of any a priori information the smallest or smoothest models are recovered.

Relief – Maximum regional difference in elevation.

Remanent Magnetization – Permanent magnetization that can be obtained by ferromagnetic material through several phenomena including thermo-, chemical and detrital remanence. Magnetization remaining after the application of magnetic field has ceased.

Remote Sensing – Study of the earth’s surface conditions and materials from airplanes and satellites by means of photography, spectroscopy, or radar.

Repeat Section – Short interval of log that is run a second time to establish repeatability and stability.

Replacement Deposit – Deposit of ore minerals by hydrothermal solutions that have first dissolved the original mineral to form a small cavity.

Reserves – Economically mineable part of a measured and/or indicated mineral resource. It includes diluting materials and allowances for losses, which may occur when the material is mined. Appropriate assessments and studies have been carried out, and include consideration of and modification by realistically assumed mining, metallurgical, economic, marketing, legal, environmental, social and governmental factors. These assessments demonstrate at the time of reporting that extraction could reasonably be justified. Reserves are sub-divided in order of increasing confidence into probable reserves and proved reserves.

Residual – Result of the subtraction of any two sets of values. If we take the difference between observed and predicted data, the resulting residual provides a quick measure of how well we did in estimating the predicted data. What is left over can be referred to as a regional residual. Had we taken the difference between our reference model and our inverted model, we would be left with our model residual.

Resistivity – Property of a material that resists the flow of electrical current, expressed in ohm-metres. The opposite of resistivity is conductivity and measures a material’s ability to conduct an electric current.

Resistivity Logs – Group of logs that are designed to make quantitative measurements of the specific resistance of a material to the flow of electric current.

Resolution – Smallest unit of measurement that can be distinguished using a particular instrument or method; based on the ability to separate two measurements which are very close together.

Resources – Concentration or occurrence of material of intrinsic economic interest in or on the earth’s crust in such form, quality and quantity that there are reasonable prospects for eventual economic extraction. The location, quantity, grade, geological characteristics and continuity of resources are known, estimated or interpreted from specific geological evidence and knowledge. Resources are sub-divided, in order of increasing geological confidence, into inferred, indicated and measured categories.

Reversal – Typical distortion of normal-resistivity logs opposite beds that are thinner than the AM spacing of which the effect is an apparent decrease in resistivity in the center of a resistive unit.

Reverse-Circulation – RC Drilling or Rotary drilling method that uses a double-walled drill pipe. Compressed air and water is forced down the space between the two pipes to the drill bit and the drilled chips are flushed back up to the surface through the centre tube of the drill casing.

Reversible Reaction – Chemical reaction which can proceed in either direction, depending on the concentration of reacting materials.

Rheidity – Ability of a substance to yield to viscous flow under large strains.

Rhyolite – Light coloured Igneous, volcanic rock, of felsic (silica-rich) composition, typically more than 69% silicon dioxide, the symbol of which is SiO2. Rhyolite is the extrusive equivalent of granite.

Richter Magnitude Scale – Objective scale for measuring earthquake energy in magnitude.

Ridge Mid-Ocean – Major linear elevated landform of the ocean floor.

RI/FS – Remedial Investigation/Feasibility Study.

Rift – Long crack for the entire thickness of the Earth’s crust formed under stress as the crust is pulled in various directions. The rift will be surrounded with normal faults on either side.

Rift Valley – Long, narrow-shaped lowland between highlands or mountain ranges created by the action of a geologic rift or fault.

Right-Lateral Fault – Strike-slip fault on which the displacement of the far block is to the right if viewed from either side.

Ring Dike – Dike in the form of a segment of a cone or cylinder.

Rip Current – Current that flows strongly away from the sea shore at intervals along the shoreline.

Ripple – Very small dune of sand or silt whose long dimension is formed at right angles to the current.

Ripple Marks – Small ridges produced on a surface of sand or mud by the movement of wind or water.

Rock Cycle – Geologic cycle emphasizing the rocks produced. Often, sedimentary rocks are metamorphosed to metamorphic rocks, or melted to create igneous rocks, and all rocks may be uplifted and eroded to make sediments, which lithify to sedimentary rocks.

Rock Flour – Glacial sediment of extremely fine ground rock formed by abrasion of rocks at the base of the glacier.

Rock Glacier – Glacier-like mass of rock fragments or talus with interstitial ice that moves downhill under the force of gravity.

Rockslide – Landslide involving mainly large blocks of detached bedrock with little or no soil or sand.

Roìche MoutonneÇe – Knob of bedrock that has been striated and rounded by glaciers, with a gentle slope facing the up-ice direction.

ROM – Run-of-mine

Rounding – Amount to which the edges and corners of a particle become worn and rounded as a result of abrasion during transportation. Referred to as angular, sub-rounded, well-rounded, etc.

Runoff – Amount of rain water directly leaving an area in surface drainage, as opposed to the amount that seeps out as groundwater.

Rupture Strength – Greatest stress that a material can sustain without fracturing at one atmosphere pressure.