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R
raise - (2) a vertical or inclined opening driven upward
from a level to connect to the level above or to explore the ground
for a limited distance above one level.
raptors - (3) birds of prey.
rare earth metals - (3) a group of widely distributed metals,
consisting of the elements scandium, yttrium, and 15 elements of
atomic numbers 57 to 71, inclusive. These metals have the same arrangements
of the two external shells of electrons in their atoms and resemble
on another closely in chemical and physical properties, being thus
most difficult to separate from each other. It is to this property,
rather that their actual rarity in nature, that they are described.
reactivity - (3) a substance's tendency to undergo chemical
reaction either by itself or with other materials with the release
of energy. Undesirable effects such as pressure buildup, temperature
increase, or formation of noxious, toxic, or corrosive by-products
may result from a substance's reactivity to heating, burning, direct
contact with other materials, or other conditions.
recharge area - (3) an area that absorbs water that eventually
reaches the zone of saturation in one or more aquifers.
reclamation - (4) an activity aimed at rehabilitating a
disturbed site to a near-natural state or an agreed post-mine level
of productivity.
recontouring - (4) reshaping a land surface.
recovery - (4) the percentage of valuable metal in the ore
that is recovered from the host rock by metallurgical treatment.
redd - (3 the spawning ground or nest of various fishes.
redox conditions - (4) a measure of the theoretical electron
activity of an environment. A high redox potential indicates aerobic
conditions. A low redox potential indicates anaerobic or
reducing conditions. See oxidation/reduction potential.
reducers (decomposers) - (3) organisms, usually bacteria
or fungi, that break down complex organic material into simple compounds.
refractory ores - (1) ores that resist the action of chemical
reagents in the normal treatment processes and which may require
roasting or other means to effect the full recovery of the valuable
minerals.
replacement growth media - (3) material below the C horizon
of the soil that can be substituted for topsoil or subsoil when
it is equal to or superior in quality as a surface cover for growing
plants on reconstructed mine surfaces.
return period - (4) the average length of time separating
events of similar magnitude. See flood recurrence interval.
revegetation - (4) as a part of reclamation, an activity
aimed at reestablishing vegetation on cleared surfaces.
right-of-way - (3) a permit or easement that authorizes
the use of lands for specified purposes, such as for a forest access
road or a power line.
rill - (3) a small, intermittent water course with steep
sides, usually only a few inches deep.
riparian area - (3) a form of wetland transition between
permanently saturated wetlands and upland ares. Riparian areas exhibit
vegetation or physical characteristics that reflect the influence
of permanent surface or subsurface water. Typical riparian areas
include lands along, adjacent to, or contiguous with perennially
and intermittently flowing rivers and streams, glacial potholes,
and the shores of lakes and reservoirs with stable water levels.
Excluded are ephemeral streams or washes that lack vegetation and
depend on free water in the soil.
roasting - (3) heating sulfide-bearing ores to release sulfur
dioxide.
rock - (4) naturally formed, solid mass of one or more minerals,
amorphous inorganic matter or organic matter. See also lithify.
runoff - (4) that part of precipitation and snowmelt that
does not infiltrate but moves as an overland flow. See also evapotranspiration
and infiltration.
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