Glossary of Rock and Mineral Terms - S
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- Composed of tiny, equi-dimensional crystals that resemble grains of sugar.
- Containing salt.
- saline deposit
- Mineral environment containing minerals formed through partial or full
evaporation of a mineral-rich, saline lake.
- saline lake
- Mineral-rich lake found in arid regions that contains a heavy salt content,
and frequently contains evaporate minerals which form as the lake evaporates.
Saline lakes may fully evaporate, in which they become dry lakes.
- Amount of salt present.
- 1) Compound formed when a metal partially or fully takes the place of
hydrogen in an acid.
- 2) The mineral Halite.
- salt dome
- Separated fold in an anticline which is plugged up with a mass of salt.
- Accumulation of small grains of rock, usually found at beaches and in desert
- A clastic rock composed of particles that range in diameter from 1/16
millimeter to 2 millimeters in diameter. Sandstones make up about 25% of all
- Six sided polyhedron, similar to a bipyramidal hexagon, but the adjoining
area at the center is diagonal between every side as opposed to being level.
Other modifications might be present. Minerals shape this way are
- Aggregate of small, flattened, overlapping crystals, as seen in fish scales.
- Describing an aggregate of scales.
- The steep cliff face that is formed by a slump.
- Crystal deformity where the top part of a prismatic crystal protrudes and is
wider than the rest of the crystal.
- Color reflections or color "flashes" present in a mineral. The
individual color flashes of Opal are known as "schillers".
- A coarse-grained, strongly foliated metamorphic rock that develops
from phyllite and splits easily into flat, parallel slabs. Type of
metamorphic rock made up of parallel layers of flaky, micaceous minerals.
- scientific law
- 1. A natural phenomenon that has been proven to occur invariably whenever
certain conditions are met. 2. A formal statement describing such a phenomenon
and the conditions under which it occurs. Also called law.
- scientific methods
- Techniques that involve gathering all available data on a subject, forming a
hypothesis to explain the data, conducting experiments to test the hypothesis,
and modifying or confirming the hypothesis as necessary to account for the
- Instrument used to determine the absolute hardness of a mineral. A mineral
is locked into position , and a Diamond pin pushes down and slightly scratched
the mineral. The amount of pressure needed for the Diamond pin to be pushed
down to scratch the mineral determines its hardness.
- sea arch
- A landform produced by coastal erosion of a prominent headland. Sea arches
form when sea caves are excavated so deeply by crashing waves that two caves
eroding on opposite sides of the headland become joined. The overlying rocky
roof is left as an arch.
- sea cave
- The notches in the sides of a prominent coastal rocky headland eroded by
- sea-floor spreading
- The formation and growth of oceans that occurs following rifting and
is characterized by eruptions along mid-ocean ridges, forming new
oceanic lithosphere, and expanding ocean basins. See also divergence.
- A conical underwater mountain formed by a volcano and rising 1000
meters or more from the sea floor.
- sea stack
- A steep, isolated island of rock, separated from a headland by the
action of waves, as when the overhanging section of a sea arch is eroded.
- A wall of stone, concrete, or other sturdy material, built along the shoreline
to prevent erosion even by the strongest and highest of waves. See also riprap.
- Altered to create a new mineral.
- secondary coast
- A coast shaped primarily by erosion or deposition by sea currents and
- secondary enrichment
- The process by which a metal deposit becomes concentrated when other
minerals are eliminated from the deposit, as through dissolution,
precipitation, or weathering.
- secondary mineral
- Mineral altered to a new form after undergoing a chemical change. An example
is a mineral in the oxidation zone that transformed into another mineral
- Able to be cut into by a knife or other sharp object. A form of tenacity.
- A collection of transported fragments or precipitated materials that
accumulate, typically in loose layers, as of sand or mud.
- sedimentary environment
- The continental, oceanic, or coastal surroundings in which sediment
- sedimentary facies
- 1. A set of characteristics that distinguish a given section of sedimentary
rock from nearby sections. Such characteristics include mineral content, grain
size, shape, and density. 2. A section of sedimentary rock so characterized.
- sedimentary rock
- A rock made from the consolidation of solid fragments, as of other
rocks or organic remains, or by precipitation of minerals from solution.
- sedimentary structure
- A physical characteristic of a detrital sediment that reflects the
conditions under which the sediment was deposited.
- sedimentation process
- Process in which sediment transforms into sedimentary rock.
- seismic gap
- A locked fault segment that has not experienced seismic activity for a long
time. Because stress tends to accumulate in seismic gaps, they often become
the sites of major earthquakes.
- seismic moment
- A numerical means of measuring an earthquake's total energy release. It is
calculated by measuring the total length of fault rupture and then factoring
in the depth of rupture, total slip along the rupture, and the strength of the
- seismic profiling
- The mapping of rocks lying along and beneath the ocean floor by recording
the reflections and refractions of seismic waves.
- seismic tomography
- The process whereby a computer first synthesizes data on the velocities of seismic
waves from thousands of recent earthquakes to make a series of images
depicting successive planes within the Earth, and then uses these images to
construct a three-dimensional representation of the Earth's interior.
- seismic wave
- One of a series of progressive disturbances that reverberate through the
Earth to transmit the energy released from an earthquake.
- A visual record produced by a seismograph and showing the arrival times and
magnitudes of various seismic waves.
- A machine for measuring the intensity of earthquakes by recording the
seismic waves that they generate.
- The study of earthquakes and the structure of the Earth, based on
data from seismic waves.
- selenides subgroup
- Group of sulfides the contain one or more true metals combined with the
- The area of the point of contact between a vein and the surrounding rock.
- Element or alloy exhibiting certain properties of the metals and certain
properties of the non-metals. They are opaque with a metallic luster, and
combine with other elements to form minerals as metals do. In all other
aspects, they act like non-metals.
- semi-metallic elements
- The semi-metallic elements are minerals belonging to the native elements
group and are composed of pure semi-metallic elements or semi-metallic alloys.
They are opaque with a metallic luster, and combine with other elements to
form minerals (i.e. Arsenides, Tellurides) the same way the metallic elements
- semi-precious stone
- Gem or gemstone used in jewelry but lacks in one or more property (such as
luster, hardness, and rarity) that would make it into a precious gemstone.
- A series is a mineral group consisting of minerals that have a nearly
identical crystal structure. The only difference between the minerals in a
series is the type of elements contained in the crystal structure of the
mineral. This means that there must be at least two defined minerals in a
series: one mineral containing one particular element, and one mineral
containing a different element. These two minerals are known as the end
members, or anchor members. In-between the end members minerals as a
combination of both anchor members exist. Sometimes, these intermediary
minerals are given names.
- The proper placement of a gem on an ornament, or the ordained area for the
placement of a gem.
- A long, narrow passage in underground mines created for the extraction of
- A sedimentary rock composed of detrital sediment particles
less than 0.004 millimeter in diameter. Shales tend to be red, brown, black,
or gray, and usually originate in relatively still waters.
- Synonym to wheat sheaf.
- shearing stress
- Stress that slices rocks into parallel blocks that slide in opposite
directions along their adjacent sides. Shearing stress may be caused by transform
- sheet silictes
- Another name for phyllosilicates. Group of silicate minerals that have each
set of tetrahedrons surrounded by three oxygen atoms, forming a sheet like
- shelly fracture
- Synonym of conchoidal fracture.
- shield volcano
- A low, broad, gently sloping, dome-shaped structure that forms over time as
repeated eruptions eject basaltic lava through one or more vents and
the lava solidifies in approximately the same volume all around.
- shock metamorphism
- The metamorphism that results when a meteorite strikes rocks at the
Earth's surface. The meteoric impact generates tremendous pressure and
extremely high temperatures that cause minerals to shatter and recrystallize,
producing new minerals that cannot arise under any other circumstances.
- The boundary between a body of water and dry land.
- short wave
- A wavelength of ultraviolet light. Many minerals display fluorescence when
exposed to shortwave ultraviolet light. Commonly abbreviated as SW.
- Radical of silicon and oxygen. Also term for any material composed of only
silicon and oxygen (and can include water), such as Quartz, Chalcedony, and
- Having been transformed into silica. An example is petrified wood, or wood
that was completely replaced by silica.
- silica group
- Group of silicate minerals (tectosilicates) composed only of silica (silicon
dioxide -- SiO2 ). The minerals in this group are all the varieties of Quartz,
Chalcedony, Opal, Tridymite, and Cristobalite (and a few rarer forms of
silicon dioxide). Although Opal contains water in addition to silica, it is
nevertheless in the silica group. The Silica Group is also known as the Quartz
- One of several rock-forming minerals that contain silicon, oxygen, and
usually one or more other common elements.
- Group of minerals containing various amounts of the elements silicon and
- silicon oxygen tetrahedron
- A four-sided geometric form created by the tight bonding of four oxygen
atoms to each other, and also to a single silicon atom that lies in the middle
of the form.
- silky luster
- Luster of minerals that have a very fine fibrous structure, causing it to
display similar optical properties to silk cloth.
- A concordant pluton that is substantially wider than it is thick.
Sills form within a few kilometers of the Earth's surface. See also dike.
A horizontal "sheet" of igneous rock interjected between rock that
was there before the igneous rock. A famous example is the Palisades Sill
right near on the western side of the Hudson River right near New York City.
- Accumulation of very small grains of rock, finer than sand.
- simple oxides
- Compounds of metallic elements combined with oxygen. The simple oxides are a
subgroup of the oxide group.
- simple sulfides
- Group of sulfides that contain one or more true metals combined with sulfur.
- A circular, often funnel-shaped depression in the ground that forms when
soluble rocks dissolve.
- Mineral deposit formed by mineral-rich spring water which comes to the
surface and loses its capacity to withhold the dissolved mineral, thereby
depositing it and forming a growing mound.
- Rutile twin - Two or more crystals that twin in a repeated pattern
("repeated twinning") as depicted in the figure below. Named after
the mineral Rutile, which most frequently exhibits this form of twinning. If
there are six repeated crystals (i.e. another three crystals are added to the
figure below in the same pattern), the agglomerate forms a circular structure,
known as a sixling.
- Aggregate synonymous with dendritic. Some references note a difference in
that skeletal is a single, tree-like entity, whereas dendritic is the same
pattern implanted in rock.
- Thick slice cut out of a solid mineral; a portion of the mineral.
- Glassy substance formed as a by-product from the smelting of metallic ores.
- A fine-grained, foliated metamorphic rock that develops from shale
and tends to break into thin, flat sheets.
- The mass movement of a single, intact mass of rock, soil, or unconsolidated
material along a weak plane, such as a fault, fracture, or bedding
plane. A slide may involve as little as a minor displacement of soil or as
much as the displacement of an entire mountainside.
- slip face
- The steep leeward slope of a dune.
- slip plane
- A weak plane in a rock mass from which material is likely to break off in a slide.
- 1. A downward and outward slide occurring along a concave slip
plane. 2. The material that breaks off in such a slide.
- To melt ores for the extraction of a valuable metal they contain.
- smooth fracture
- Synonym of even fracture
- The lowest point at which snow remains year-round.
- The top layer of the earth's surface, which is composed of tiny rock
particles mixed together with decaying organic matter.
- soil horizon
- A layer of soil that can be distinguished from the surrounding soil by such
features as chemical composition, color, and texture.
- soil profile
- A vertical strip of soil stretching from the surface down to the bedrock and
including all of the successive soil horizons.
- solid solution
- A series formed when there are minerals in-between two isomorphous minerals.
An example is the Plagioclase Feldspar group, which contains Albite and
Anorthite as the anchor minerals, and minerals varying in amounts of those two
minerals. Solid solutions may also be composed of minerals with a definite
structure where one element may be minutely replace by another, but is too
insignificant to be mentioned in the structure of that mineral.
- Transforming from a liquid state to a solid state.
- A form of creep in which soil flows downslope at a rate of 0.5 to 15
centimeters per year. Solifluction occurs in relatively cold regions when the
brief warmth of summer thaws only the upper meter or two of regolith, which
becomes waterlogged because the underlying ground remains frozen and therefore
the water cannot drain down into it.
- Able to be dissolved. Solubility is the condition of being soluble.
- Group of silicate minerals that are composed of groups of two tetrahedrons
where one of the oxygen atoms is shared by both tetrahedrons; the other three
oxygen atoms are not shared by another tetrahedron.
- The process by which a given transport medium separates out certain
particles, as on the basis of size, shape, or density.
- source rock
- A rock in which hydrocarbons originate.
- Any non-metallic, lightly colored mineral with good cleavage.
- specific gravity
- The ratio of the weight of a particular volume of a given substance to the
weight of an equal volume of pure water.
- A mineral or rock of interest to collectors or scientists.
- Plural of spectrum.
- Having to do with the spectrum
- Device used to observe and record spectral changes.
- Device used to to measure the brightness of different portions of the
- Device, such as a prism, which refracts white light and produces a spectrum
which can be observed.
- The science and study of the spectrum.
- Composite of white light, which are the colors of the human eye can see. The
spectrum is composed of the colors red, orange, yellow, green, blue, indigo,
and violet in that order.
- A mineral deposit of calcium carbonate that precipitates from solution in a
- Prism with wedge shaped corners, formed from a bipyramid that did not
- spheroidal weathering
- The process by which chemical weathering, especially by water,
decomposes the angles and edges of a rock or boulder, leaving a rounded form
from which concentric layers are then stripped away as the weathering
- Aggregate consisting of rounded, ball like structures composed of radiating
crystals. Spherulite is term ussed to describe any mineral composed of
- spinel twin
- Form of contact twinning, in which two octahedral crystals that twin at the
base, as depicted in the figure below. Named after the mineral Spinel, which
most frequently exhibits this form of twinning.
- A narrow, fingerlike ridge of sand that extends from land into open water.
- splendent luster
- Synonym of metallic luster.
- splintery habit
- Crystal habit where crystals are long, thin, straight splinters.
"Splintery" also describes an aggregate composed of such crystals.
- splintery fracture
- Fracture forming elongated splinters. All fibrous minerals fall into this
- Able to withstand normal environments without disintegrating.
- An icicle-like mineral formation that hangs from the ceiling of a cave and
is usually made up of travertine, which precipitates as water rich in
dissolved limestone drips down from the cave's ceiling. See also stalagmite.
- Aggregate composed of long, icicle-like formations, like stalactites.
- A cone-shaped mineral deposit that forms on the floor of a cave and is
usually made up of travertine, which precipitates as water rich in dissolved
limestone drips down from the cave's ceiling. See also stalactite.
- Shaped as a stalagmite, as a tall-domed structure. Many times confused with
the term stalactitic, and many times substituted for that word.
- star dune
- A dune with three or four arms radiating from its usually higher
center so that it resembles a star in shape. Star dunes form when winds blow
from three or four directions, or when the wind direction shifts frequently.
- staurolite twin
- Form of penetration twinning where two monoclinic crystals form
interpenetrating twins at 90º, forming a cross, as depicted in the figure
below. Named after the mineral Staurolite, which most frequently exhibits this
form of twinning. (Staurolite crystals may also twin at angles other than
90º, such as 60º.)
- Synonym of radiating.
- Body of exposed igneous rock that intruded a layer of underground
sedimentary rock, and is smaller than around 40 square miles (around 100
- Small piece of rock; may or may not refer to ornamental material.
- The change in the shape or volume of a rock that results from stress.
- The behavior of having mineral sediments embedded in sedimentary rock.
- A cone-shaped volcano built from alternating layers of pyroclastics
and viscous andesitic lava. Stratovolcanos tend to be very large and
- Layer of sedimentary rock compromised of one rock type. Layers of strata
containing different rocks may form parallel bands of different rock.
Strata is the plural form of stratum.
- The color of a mineral in its powdered form. This color is usually
determined by rubbing the mineral against an unglazed porcelain slab and
observing the mark made by it on the slab.
- streak plate
- Unglazed piece of porcelain, such as a tile, used to test a mineral's streak
- A body of water found on the Earth's surface and confined to a narrow
topographic depression, down which it flows and transports rock particles,
sediment, and dissolved particles. Rivers, creeks, brooks, and runs are all
- stream discharge
- The volume of water to pass a given point on a stream bank per unit of time,
usually expressed in cubic meters of water per second.
- stream terrace
- A level plain lying above and running parallel to a stream bed. A stream
terrace is formed when a stream's bed erodes to a substantially lower level,
leaving its floodplain high above it.
- The force acting on a rock or another solid to deform it, measured in
kilograms per square centimeter or pounds per square inch.
- Exhibiting tiny parallel lines or grooves.
- 1.) One of a group of usually parallel scratches engraved in bedrock by a glacier
or other geological agent.
2.) Tiny, parallel lines seen on some crystal faces.
- 1. ) The horizontal line marking the intersection between the inclined plane of a
solid geological structure and the Earth's surface.
2. The compass direction
of this line, measured in degrees from true north.
- strike-slip fault
- A fault in which two sections of rock have moved horizontally in
opposite directions, parallel to the line of the fracture that divided
them. Strike-slip faults are caused by shearing stress.
- structural geology
- The scientific study of the geological processes that deform the Earth's
crust and create mountains.
- 1.) The form of a mineral based on the way its molecules are arranged.
2.) Features exhibited in rock portions, for example flow banding and bedding.
- Short and fat. Used in describing crystals.
- Small jewel placed on an ornament, such as an earring. May also refer to the
verb form of setting with a stud. Sometimes additionally refers to a cable
that holds together a metallic ornamental chain, such as a necklace.
- subconchoidal fracture
- Mineral fracture that falls somewhere between conchoidal and even; being
smooth with irregularly rounded corners.
- The sinking of an oceanic plate edge as a result of convergence with
a plate of lesser density. Subduction often causes earthquakes and
creates volcano chains.
- The next level of mineral classification after categorization in groups.
- To go from a solid state directly to a gaseous state without becoming
- sub metallic luster
- Luster of opaque to nearly opaque minerals with very good reflective
- The lowering of the Earth's surface, caused by such factors as compaction, a
decrease in groundwater, or the pumping of oil.
- Group of minerals that contains one or more metallic element in addition to
the sulfate radical (SO4). All sulfates are transparent to
translucent and soft. Most are heavy and lightly colored, and some are soluble
in water. Rarer sulfates exist containing substitutions for the sulfate
radical, such as the chromates, where it is replaced by a chromate radical
(CrO4). The sulfates can be divided into the Hydrous sulfates and
the Anhydrous sulfates. The chromates are usually classified as a sub-group of
- Group of minerals that are compounds of one or more metallic elements
combined with the non-metallic element sulfur. The sulfur acts as a semi-metal
when it combines to form a sulfide mineral. In some sulfides, the semi-metals
arsenic, antimony, selenium, and tellurium substitute for the sulfur. There
are different types of sulfides known as: Simple sulfides, Arsenides,
Antimonides, Tellurides, Selenides, and Sulfosalts.
- Group of sulfides that contain one or more true metals, sulfur, and either
the semi-metals antimony, arsenic, or bismuth. They are generally soft, have a
metallic luster, and are heavy and uncommon.
- sulfuric acid
- Chemically H2SO4, it is a corrosive, oily, acid used
for manufacturing chemicals, medicine, paints, detergents, and explosives. It
is a very destructive liquid and will destroy many minerals.
- surface wave
- One of a series of seismic waves that transmits energy from an
earthquake's epicenter along the Earth's surface. See also body wave.
- To flow more rapidly than usually. Said of a glacier.
- surrounding rock
- The rock surrounding a vein or embedded crystal.
- suspended load
- A body of fine, solid particles, typically of sand, clay, and silt, that
travels with stream water without coming in contact with the stream bed.
- suture zone
- The area where two continental plates have joined together through continental
collision. Suture zones are marked by extremely high mountain ranges, such
as the Himalayas and the Alps.
- swallowtail twin
- Form of penetration twinning in which two monoclinic crystals twin to form a
v-shaped model, as depicted in the figure below. This form of twinning is most
frequently seen on the mineral Gypsum.
- S wave (abbreviation for secondary wave)
- A body wave that causes the rocks along which it passes to move up
and down perpendicular to the direction of its own movement. See also P
- S-wave shadow zone
- The region within an arc of 154° directly opposite an earthquake's
epicenter that is marked by the absence of S waves. The S-wave shadow
zone is due to the fact that S waves cannot penetrate the liquid outer core.
See also P-wave shadow zone.
- Igneous rock containing alkali feldspars. Contains mica and pyroxene
- Exact proportion from an intermediate center horizontal line, vertical line,
or central point. If an object has symmetry, than it can be rotated or flipped
and appear the the exact same way it was before the rotate or flip. The axes
(x axis and y axis) are imaginary lines drawn through the center of the shape;
the x axis going in a horizontal direction, the y axis going in a vertical
direction. There are three types of symmetry:
a) Symmetry about a center point: Will retain the same shape even
if flipped over both the x and y axes. Can be rotated 90° and will still
retain the same shape.
b) Symmetry about the x axis: Will retain the same shape if flipped
over the the x axis.
c) Symmetry about the y axis: Will retain the same shape if
flipped over the the y axis.
- A concave fold, the central part of which contains the youngest
section of rock. See also anticline.
- Man made. Synthetic gems are created using molten chemicals to solidify and
form the gem.