Glossary
of Geological Words and Terms Associated with
Geological
Information Specimen Content and
Origin
Adamantine: transparent minerals with a very
high luster and ability to reflect and transmit light
Adularia: a feldspar of (potassium
aluminum silicate) found in moonstone
Adularescence: a shimmering play of
light reflecting from within a stone, such as in moonstone
Aggregate: a composite of rocks and
minerals such as stream beds that include sand and boulders
which over time can form layers or larger boulders that
have been naturally cemented together
Almandine: an iron aluminum
silicate mineral of the garnet group which is deep red to
reddish purple
Aluminum: a member of the periodic
table of elements (Al,13) and the most abundant of all of
Earth’s metals, it is very flexible and melts at a low
temperature
Alluvial: deposits of clay, silt,
sand and gravel left by flowing streams in a river valley
or a delta
Amesite: magnesium, aluminum,
silicon hydrogen oxygen; a product of low grade
metamorphism of aluminum, magnesium-rich rocks, a
phyllosilicate, layered or sheet, mica-like, in the
serpentine group
Ametrine: a natural occurring
variety of quartz that is a mixture of purple amethyst and
yellow citrine in one
Amorphous: having no definite form,
shapeless like a cloud
Anisotrophic: lacking consistent
hardness on all surfaces or asymmetry of crystal layers or
direction
Apatite group: represents the
phosphate minerals; chlorapatite, fluoapatite and hydroxyl
apatite. These minerals may often replace one another, the
most common being fluorapatite
Aqueous Solutions: a solution in
which water is the solvent, such as minerals that are
dissolved in water
Asbestos: a natural occurring
mineral which crystals form long, thin fibers that are
resistant to heat
Asterism: is a star effect in
certain minerals caused by light traveling perpendicular to
the crystal faces along tiny fiber-like inclusions, some
stones have four faces such as black star dioptase and some
have six like star ruby
Asymmetry: the absence of symmetry,
not equal sided or balanced
Atom: the smallest particle that is
characterized as a chemical element
Augite: a crystal that
consists of (calcium magnesium iron silicate) found in
igneous and metamorphic rock
Aventurecense: a metallic, glitter
effect seen in certain stones caused by minute mineral
platelets within the stone
Banding: a layering of colors or
shades within a stone due to the way in which the formation
grew, such as malachite, azurite, some agates and
chalcedony
Barium: a chemical element (Ba,56)
silvery, metallic, alkaline metal not found alone but with
other minerals
Beryl Group: (beryllium aluminum
silicate) Forms as a six sided crystal. Members are emerald
(green), aquamarine (aqua), morganite (pink), heliodor
(yellow), bixbite (red)
Beryllium: a member of the periodic
table of elements (Be,4), steel gray, light weight, yet
brittle, alkaline earth metal. Used as a harden in alloys
Boron: a member of the periodic
table of elements and a trivalent nonmetallic element which
occurs abundantly in the evaporative ores borax and
ulexite. It is also an important element for plant and
animal life
Borosilicate: (silica boron oxide)
a form of glass
Botryodial: a mineral formation,
translucent or opaque, which has a surface texture that
resembles a bunch of grapes or smooth bubbles
Cabochon: a lapidary term used to
describe a stone that has been cut with a convex top and a
flat bottom
Calcite: (calcium carbonate) a
common mineral in the Earth’s surface forming in
sedimentary rocks and metamorphic limestone, occurring in
veins, deposits and as stalactites and stalagmites
Calcium: a member of the periodic
table of elements (Ca,20), and a common alkaline earth
metal which is essential for all living organisms
Carbon: a member of the periodic
table of elements (C,6) and the non metallic basis of all
known life
Carbonate: a salt or ester of
carbonic acid, carbonate minerals are those containing the
carbonate ion
Calibrated: a lapidary term
referring to accepted standardized measurements or sizes of
cut stones
Cavities: open pockets within a
rock or mineral deposit that allow the collection of other
elements and water to then be able to form into another
formation over time, such as drusy crystals
Chatoyant: an optical reflecting
effect found in certain gemstones which have a fibrous,
inclusion structure that displays a silky sheen
Chert: a fine grained, silica-rich,
cryptocrystalline, sedimentary rock and a form of quartz,
the name jasper is used for the more vivid colors of chert,
aventurine is also a for of mica rich chert
Chlinoclore: a member of the
chlorite group of phyllosilicates (magnesium iron aluminum
silicate hydroxide) formed in metamorphic rock
Chlorine: a member of the periodic
table of elements (Ci,17), in the salt forming halogen
series and the most abundant dissolved ion in ocean water
Chlorite Group: a group of
phyllosilicate minerals formed in a wide range of pressure
and thermal conditions in metamorphic, igneous and
sedimentary rock
Chlorovanadite: a compound of
73.15% lead,10.79% vanadium,13.56% oxygen and 2.5% chlorine
Chromium: a member of the periodic
table of elements (Cr,24), which is steel-gray, lustrous,
malleable, hard metal with a high melting point
Cobalt: a member of the periodic
table of elements (Co,27) and a silver-gray metal found in
various ores. It is used in high strength alloys and in
pigments, paints and varnishes
Colloidal: a mixture of particles
dispersed in two separate phases; a dispersed phase and a
continuous phase, the dispersed phase is distributed evenly
throughout the continuous phase
Columnar: similar to fibrous, long,
slender prisms often with parallel growth
Contact Metamorphous: typically
occurs around intrusive igneous rock as a result of
temperature increase caused by the intrusion of magma into
cooler rock
Continental Plates: The Earth’s
crust and mantle are in constant motion, pulling apart,
colliding together, moving sideways, causing valleys,
mountains rifts, folds and fault lines. Over time this has
moved and shaped the continents. There are 14 main plates
with smaller sub plates.
Copper: a member of the periodic
table of elements (Cu,29) and a valuable element for plant
and animal life, a malleable metal with excellent
electrical conductivity and also used as an alloy to
strengthen other metals
Cordierite: (magnesium aluminum
silicate) also known as iolite, a blue-violite translucent
to transparent mineral
Corundum: a crystalline form of
aluminum oxide and a rock forming mineral, occurring as a
mineral in mica schist, gneiss and some marbles in
metamorphic terrains, naturally clear but when certain
impurities are present it can also be known as ruby or
sapphire, with a hardness of 8-9 the clear variety is
commonly used as an abrasive for items such as sand paper
etc.
Crocidolite: naturally occurring
long fine crystal fibers (known as asbestos) which are the
basis of the pseudomorh chalcedony known as tiger eye
(brown) and hawk eye (blue), the mineral fibers are
silicified (replaced by quartz-silica)
Crusts: minerals that form on the
surface of a host rock in layers, these layers can have a
crystal or botryoidal habit
Crystal: a body that is formed by
the solidification of a chemical element, compound or a
mixture and has a regularly repeating internal arrangement
of its atoms and often external plane faces
Crystalline: rocks that display a
definite crystal orientation
Crystallization: the process by
which liquid, elemental, mineral solutions are replaced
over time by a solid formation
Crystallographic: the scientific
study of crystals. Determining the arrangements of atoms in
crystals through the analysis of the defraction patterns
from a light beam source
Cryptpcrystalline: crystals that
are so minute that they can only be seen through a
microscope
Deposits: the natural laying down
or accumulation of minerals and elements over time which
leads to a large body of ore
Dolomite: (calcium magnesium
carbonate) found in sedimentary rock of a limestone base
Drusy: a crystal formation that
grows as a crust or cavity filling and has very small
crystals packed close together like grains of sugar on the
surface of the host rock. These formations have allot of
sparkle and can be found in a wide range of color, hardness
and mineral composition
Element: a chemical element is a
type of atom that is defined by its atomic number, which is
the number of protons in its nucleus
Emerald: (beryllium aluminum
silicate) A member of the beryl family, the green coloring
is due to trace amounts of chromium
Encrusted: a type of formation in
which minerals grow in a layer over the surface of a host
rock or inside of a cavity or vein within a host rock
Enhancement: there are many gem
enhancement classifications used today to improve and even
design colored gemstones; bleaching, coating, dying,
filling heat treating, impregnation, irradiation,
diffusion, lazering and waxing
Fabrication: the method of building
jewelry by hand from metal sheet and wire with many
different gages (thickness) and shapes; flat, round,
square, triangular, beaded, etc.
Faceted: a method of cutting
transparent or translucent gemstones that produces flat
surfaces on geometric shapes a very precise activity done
on a faceting machine over a period of several hours
Feldspar: (aluminum, silicate,
sodium, potassium, iron, calcium, barium) Found in varying
combinations of these elements and the most abundant group
of minerals found in Earth’s crust mostly in igneous rock
like granite and in metamorphic and sedimentary rock having
a wide use in industrial applications today such as glass
ware, earthenware, floor tiles, etc.
Feldspathoids: a group of
aluminosilicate minerals similar in composition to
feldspars but having a lower silica-alkali ratio or
containing chloride, sulfide, sulfate or carbonate,
specific to igneous rock
Fibers / Fibrous: minerals
constructed of fine, usually parallel threads or fibers
which can be very flexible, many mineral fibers are changed
over time due to heat, silification or pressure and form a
chatoyant effect within a specimen
Flaw: an imperfection in physical
form or structure, such as a mineral inclusion, crack or
weakness
Flintknapper: An individual who
shapes flint or other stones for the purpose of making a
weapon or tool is a flintknapper. A hard stone (hammer
stone) is used to shape another stone that has a particular
way of fracturing. Each blow causes a piece to flake away
revealing a very sharp edge until the desired shape and
size is achieved.
Fluorine: a member of the periodic
table of elements (F,9) and the most electronegative of all
of the elements, a pale yellow-brown gas which is poisonous
and can cause burns only in its purist form, as a mineral
specimens it is not harmful
Fool’s gold: (iron sulfide) The
mineral iron pyrite with its metallic, brass-yellow color
can sometimes resemble gold
Formation: in geology referring to
the types of rock formations such as; igneous, sedimentary
and metamorphic. In smaller rocks or crystals it refers to
the individual classification and character of any given
specimen and the way it presents itself
Fossil: mineralized preserved
remains of animals, plants and other organisms found in
rock formations and sedimentary layers allowing for the
study of geological time
Fracture: In crystalline materials,
individual crystals can fracture without the body actually
separating. Fracture planes can be a natural part of a
formation or specimen. The cleavage of a stone is a result
of the natural way in which it will fracture.
Gama-Ray Irradiated: a form of
electromagnetic radiation or light emissions of a specific
frequency produced from subatomic particle interaction,
gamma rays release electrons from their normal location in
the gemstone, the color change depends on where the
electrons relocate and on the charge of the atoms near
them, this controls the way the stone absorbs light and
that dictates its color
Garnet Group: almandine-deep red
(iron aluminum silicate); andradite-red, green, yellow,
brown, black (calcium iron silicate); grossular-clear,
white, green, yellow,pink, brown, orange and orange-red
(calcium aluminum silicate); pyrope-deep red to almost
black (magnesium aluminum silicate); spessartine-brown,
orange and pink (manganese aluminum silicate);
uvarovite-green (calcium chromium silicate)
Gem: a precious or semiprecious
stone cut and polished for ornament
Gemstone: a mineral or petrified
material that can be cut, polished and set into jewelry
Gemology: the science of
identifying and evaluating gemstones
Geode: A geode rock formation
usually has an internal cavity lined with crystals or
filled with a banded, lacy mineral body or a botryoidal
formation. The outside of the geode is usually limestone or
related rock and the interior contains quarts crystals or
chalcedony deposits. A geode is cut in half to display the
interior. Some specimens that have a drusy formation are
cut into individual stones and set into jewelry.
Geology: a science that studies the
structure of the Earth and the forces that shape it,
including composition, structure, physical properties and
geological processes
Gneiss: a common type of rock that
forms from grains of preexisting igneous or metamorphic
rock in bands or layers (foliated) and re-crystallized by
metamorphic process
Goethite: (iron oxide) Brown iron
ore found in many types of formations and environments
worldwide
Gold: a member of the periodic of
elements (Au,79) and a highly valued precious metal that
occurs as nuggets, grains and veins in rocks and in
alluvial deposits such as creaks and washes, It is a soft,
malleable and bright yellow
Grainy Masses: a mineral,
crystalline aggregate, rough or fine grained such as
granite
Granite: a common, widely
occurring, intrusive, igneous rock of hard, grainy,
crystalline, texture, consisting of quartz and orthoclase
or microcline
Granular: organic or inorganic
material that has a small particle size such as grains of
sand
Habit: the growth conditions and
characteristic features of a rock or crystal formation
Hardness: each crystal, mineral or
stone has its own hardness, determining the hardness of a
stone is done by the scratch method used in the Mohs Scale,
a harder material will scratch a softer material
Heat Treatment: used to lighten,
darken or alter a stones color
Hydrated: In inorganic chemistry
hydrates contain water molecules that are bound to a metal
center or crystallized with the metal complex.
Hydrocarbons: In organic chemistry
a hydrocarbon is an organic compound consisting entirely of
hydrogen and carbon.
Hydrogen: a member of the periodic
table of elements (H,1) and an odorless, colorless,
nonmetallic, tasteless, and highly flammable, diatomic gas,
It is the lightest and most abundant element in the
Universe
Hydrothermal: the transport and
circulation of water deep within the Earth’s crust from hot
areas to cool areas, such as hot springs or geysers or when
hot magma comes in contact with groundwater
Hydrous: chemically combined with
water in crystallization
Hydroxide: consisting of oxygen and
hydrogen atoms
Hydroxyl: an oxygen atom and a
hydrogen atom connected by a covalent bond (a form chemical
bonding that is characterized by the sharing of pairs of
electrons between atoms)
Igneous Rock: rock that forms as a
result of volcanic activity, below the surface as intrusive
or on the surface as extrusive, this magma can be derived
from preexisting rock beneath the surface of the Earth’s
crust
Impurities: In mineralogy
impurities are the different minerals and chemical elements
that give a rock or crystal its color.
Inclusions: In gemstones inclusions
are smaller minerals or mineral fibers that are imbedded
within the specimen.
Inlay: a form of stone cutting and
setting in jewelry in which stones are cut to fit exactly
into a channel or compartment, then the stones are set in
place with strong epoxy and the surface of the stones and
the metal are both sanded down to a flush finish
Intrusive Rock: an igneous rock
formation that forms below the surface of the Earth as a
result of molten magma flows, it solidifies before it
reaches the surface and may or may not be crystallized
Inorganic: composed of matter other
than plant or animal
Iridescence: a play of colors
producing a rainbow effect or hue change on a surface when
viewed from different angles caused by multiple reflections
from multi layered, semitransparent surfaces
Iron: a member of the periodic
table of elements (Fe,26), a heavy malleable, ductile,
magnetic metal, chiefly found in igneous rock and the
heaviest, most widely used metal
Iron Oxide: forms as a result of
iron being exposed to the oxygen in the atmosphere
Kimberlite: potassium-rich volcanic
rock occurring in the Earth’s crust and known for
containing diamonds, named after the town of Kimberly,
South Africa where the diamond rush of 1871 began
Knobby Swirls: some rock formations
grow with bubbly-knobby (botryoidal) and banded swirls
together, suck as azurite and malachite
Labradorescence: an iridescent
sheen, color display or optical phenomenon present in
labradorite and caused by feldspar minerals, colors change
as the stone moves
Lacing: as in lace agate,
crystalline layers form one on another and the effect is
the look of old fashioned lace
Lead: a member of the periodic
table of elements (Pb,82) and a soft, heavy, toxic and
malleable poor metal, found in copper, silver and zinc
deposits
Limestone: a sedimentary rock
composed largely of the mineral calcite
Lithium: a member of the periodic
table of elements (Li,3) and a soft silver-white alkali
metal, the lightest and least dense metal and occurs in
pegmatite minerals
Luster: the way light interacts
with the surface of a crystal, rock or mineral in radiance,
gloss or brilliance
Macrocrystalline: having crystals
large enough to be seen with the unaided eye
Magnesium: a member of the periodic
table of elements (Mg,12) and an alkaline earth metal
essential to all living cells, a silvery-white, lightweight
metal, found in over sixty minerals, dolomite, magnesite,
brucite, talc, carnallite and olivine are of commercial
importance
Manganese: a member of the periodic
table of elements (Mn,25) often found in combination with
iron as well as many minerals, a required trace mineral for
all living organisms
Mantle: the region of the Earth’s
interior between the crust and the core, which contains
hot, dense silicate rocks, 1,800 miles thick and is 70% of
the Earth’s volume
Marble: a metamorphic rock which
forms as a result of metamorphism of limestone which is
mostly calcium carbonate or dolostone (dolomite), different
minerals give marble its different colors, formed under
intense heat and pressure
Massive: shapeless, no distinctive
external crystal shape
Metamorphic Rock: makes up a large
part of the Earth’s crust and is formed under the surface
in high temperatures and under great pressure
Mica: sheet silicate
Mica Group: group of sheet silicate
minerals; true micas, brittle micas and inter
layered-deficient micas, this combination of minerals is
too numerous to mention here
Mica-Schist: a metamorphic
silica-rich rock, most commonly containing aluminum and
potassium, forms in thin flaky sheets as a result of
preexisting igneous and sedimentary rock being altered
again by heat and pressure
Microcline: a potassium-rich,
alkali feldspar, formed in igneous rock of granite and
pegmatites, amazonite is a green variety of microcline
Microcrystalline: a small, fine
crystal structure that is only visible through a microscope
Minerals: a naturally occurring
substance formed by geological processes that has a
characteristic chemical composition, a highly ordered
atomic structure and specific physical properties
Mineral Fibers: aggregate minerals
constructed of fine, parallel threads compacted together,
some specimens have a cloth-like flexibility often
compacted together under heat and pressure and silicified
as in the case of crocidolite asbestos which forms the
mineral tigereye, rutile is also another example
Mohs Scale: a scale used to
determine the hardness of a mineral in which a scratch test
is used, a harder material is used to scratch a softer
material, created in 1812 by Frederich Mohs. Talc has a
hardness of 1 and diamond a hardness of 10
Molybdate: a compound containing an
oxoanion (a negatively charged poly atomic ion that
contains oxide)
Molybdenum: a member of the
periodic table of elements (Mo,42) and has a very high
melting point and is used in high strength steel alloys,
found in trace amounts in plants and animals
Muscovite: also known as common
mica and a phyllosilicate of aluminum and potassium, found
in granites, pegmatites, gneiss and schists and as a
contact metamorphic rock, the green chromium-rich variety
is called fuchsite
Nickel: a member of the periodic
table of elements(Ni,28) and a silvery, white metal which
is hard and ductile, used in coins, for plating brass and
iron and as a high performance alloy
Nitrogen: a member of the periodic
table of elements (N7) and a colorless, odorless,
unreactive gas that forms about 78% of the Earth’s
atmosphere
Olivine: known also as peridot
(magnesium iron silicate) and found in lava fields
worldwide and in meteorites
Opaque: non transparent or
translucent; impermeable to light; not allowing light to
pass through
Ore: the earthen-material or
“mother rock” that holds valuable elements, minerals or
metals in deposits in the Earth’s crust, which is extracted
in the mining process
Organic: matter that comes from a
recently living organism which is subject to decay, an
organic compound whose molecules contain carbon
Orthoclase: an important,
tectosiliicate mineral also known as feldspar which is
common in pegmatite, igneous, granite and has a monocline
crystal structure and a straight cleavage, potassium and
sodium are important minerals in these formations
Overlay: in jewelry fabrication, it
is the process of soldering a special design sheet of metal
over another, such as a textured or cut out design in gold
over silver
Oxide: a chemical compound
containing an oxygen atom and other elements, oxides result
when elements are oxidized by air, most of the Earth’s
crust consists of oxides
Oxidation: a chemical reaction that
occurs when a metal, such as iron, meets a gas such as
oxygen; the result being rust, oxidation is the transfer of
electrons from the metal to the gas
Pegmatite: a coarse-grained igneous
rock that has a grain size of 20 mm or more and which
consists of quartz, feldspar and mica which all form
granite
Periodic Table of Elements: a
tabular method of displaying the chemical elements credited
to Russian chemist Dmitri Mendeleev in 1869 and used to
classify, systematize and compare the many forms of
chemical behavior
Petrified: a condition in which all
organic materials, within a structure, have been replaced
with minerals (most often a silicate such as quartz), while
retaining the original structure
Phosphate: in inorganic chemistry,
it is a salt of phosphoric acid
Phosphoric Acid: an inorganic
mineral acid, also known as orthophosphoric acid or
phosphoric (V0) acid
Phosphorus: a member of the
periodic table of elements (P,15) and a multivalent
nonmetal of the nitrogen group found in inorganic phosphate
rock and an essential element for all living cells,
phosphorous compounds are also used in explosives,
detergents, fertilizers, fireworks, matches, pesticides and
toothpaste
Phyllosilicate: the formation of
silica sheets that grow in layers and are held together
with a weak bond that allows them to flake apart easily,
this includes mica, talc, clay minerals and muscovite
Plagioclase: within the felspar
family it is an important tectosilicate series of minerals
which has two cleavage angles. Sodium and calcium are
important minerals in its structure which originates from
igneous rock.
Placer: a deposit of sand or gravel
in the bed of a river or lake, containing particles of
valuable material such as gold or diamonds
Plechorism: an optical phenomenon
in which a stone will appear to have different colors when
observed at different angles as when light travels on
different paths and at different speeds on the crystal
plains, there will be polarizations, each with there own
color
Polymorph: the ability of a
material to exist in more than one form or crystal
structure
Potassium: a member of the periodic
table of elements (K,19), and a soft silvery-white,
metallic, alkali metal that occurs naturally bound to other
elements and sea water
Pseudomorph: a mineral compound in
which the main component is substituted for another while
keeping its original appearance and dimensions
Pyrite: iron pyrite is iron sulfide
and its crystals form as shinny, brass-gray cubes, often
referred to as “Fool’s Gold”
Pyrope: a type of garnet in the
garnet family (magnesium aluminum silicate), which ranges
in color from fire-red, deep red, violet-red to almost
black
Quartz Family: Silicon and oxygen
are the two most common elements in the Earth’s crust
thereby making the quartz family the largest of all groups.
Silicon dioxide forms as amethyst, ametrine, citrine, rose
quartz, smokey quartz, chalcedony, agate, onyx, sardonyx,
carnelian, chrysoprase, chert, aventurine, jasper and
tigereye.
Radiating Cluster: a crystal of any
variety that grows in a radiating formation in which the
crystals start at one point and fan out in all directions,
they can be flat or three dimensional and there can be one
or several clusters within a specimen
Radiation: the emission of energy
as electromagnetic waves or as moving subatomic particles,
especially high-energy particles that cause ionization;
heat, light, electricity, etc.
Radium: a member of the periodic
table of elements (Ra,88), and a radioactive element and an
alkaline earth metal that is found in trace amounts in
uranium ore
Refractive Index: the measure of
the bending of a ray of light when passing from one medium
to another
Rhyolite: a silica-rich, igneous,
extrusive rock formed in highly viscous lavas that have
cooled more slowly consisting mostly of quartz, alkali
feldspar and plagioclase feldspar
Riebeckite: dark blue elongated
fibrous crystals found in granites, syenites, schists and
iron formations known as crocidolite which is blue asbestos
Rock: a natural occurring aggregate
of minerals which can be formed by igneous, sedimentary or
metamorphic processes
Rubellite: one of the six members
of the tourmaline group which has a pink color due to
manganese
Ruby: a pink or red variety of
corundum, aluminum oxide, with chromium giving it its pink
or red color, the most valuable stones have the deepest red
color and a presence of some mineral fibers is of value as
proof of non treatment (heat treatment), a hardness of 9 on
the Mohs scale, see corundum above
Rutile: a mineral fiber composed
mostly of (titanium dioxide) which can grow on the inside
or the outside of another mineral or crystal (an accessory
mineral) formed in high pressure and high temperature
metamorphic and igneous rock
Schist: a group of metamorphic
rocks derived from clays, muds, silts and fine grained
igneous rock and containing foliated minerals such as mica,
talc, and graphite
Sediment: any particulate matter
that can be transported by fluid flow and which is later
deposited as a layer of solid material, it can also be a
result of particles settling after they are suspended in a
still body of liquid
Sedimentary Rock: Sedimentary rock
shows the record of the history of the surface of the
Earth. As layers of silt, sand, gravel and boulders,
usually from silicate minerals, are laid down from rivers
and streams, conglomerate layers are formed. As lakes and
oceans evaporate they leave behind minerals, microscopic
sea life and fossils. Limestone, shale, dolomite and
sandstone are the result. Volcanic activity, climate and
atmosphere have also contributed to the formation of
sedimentary rock.
Shale: a fine-grained sedimentary
rock made of clays, muds and silts
Sheen: a glossy, glistening or
satiny surface
Sheet Silicates: also called
phyllosilicates (phyllo means leaf like), these minerals
form in thin sheets or layers such as mica and talc
Shiller: an optical color effect
seen in a stone which is caused by a ray of light entering
a layer and being refracted back and forth by deeper layers
within the stone, as the wavelength travels it changes
speed and the resulting color is due to the thickness and
the orientation of the layers in the stone
Silica: silicon dioxide
Silica Group: group of silicate
minerals composed only of silicon dioxide such as; quartz,
agate, chalcedony, onyx, carnelian, chrysoprase, tiger eye,
sardonox, citrine, amethyst, ametrine, rose quartz, smokey
quartz etc.
Silicate: Silicate minerals are
those containing silicon dioxide. The largest class of
minerals composing 90% of Earth’s crust. Approximately 30%
of all minerals are silicates.
Silicic: magma or igneous rock rich
in silica, granite and rhyolite are typical silicic rock
Silver: a member of the periodic
table of elements (Ag,47) and a soft, white, lustrous,
precious metal, most silver is a byproduct of copper, gold,
lead and zinc mining
Slab / Slabbing: One lapidary term
used to describe the process of cutting a stone is
slabbing. A rock or crystal is usually first cut open or
trimmed on a slab saw before moving on to the grinding
process, which forms the basic shape. A slab saw is a thin
round flat disc of steel that is used with water or other
cooling lubricants. The rim of the blade is embedded with
diamond grit.
Smithsonian National Gem and Mineral
Collection: The National Gem and Mineral
Collection is one of the most significant collections of
its kind in the world. The collection includes some of the
most incredible gems and minerals ever found. There are
over 375,000 specimens in the museum as well as a research
collection used by scientists around the world.
Sodalite: (sodium aluminum
silicate) a feldspathoid well known for its deep, royal,
blue color and sodium content, found in Canada and
Greenland and has a hardness of 5.5-6 on the Mohs scale
Sodium: a member of the periodic
table of elements (Na,11) and a soft, white, highly
reactive element, an alkali metal which quickly oxidizes in
air and is abundant in the Earth, a component of many
minerals and it is also an essential element for animal
life
Sorosilicate: any member of a group
of compounds with structures that have two silicate
tetrahedrons (a central silicon atom surrounded by four
oxygen atoms at the corners of a tetrahedron) linked
together, because one oxygen atom is shared by two
tetrahedrons, the chemical formula contains Si207, as in
hemimorphite
Specimen: In geology a specimen
refers to any particular item or part typical of the whole.
As a gem, crystal or mineral a specimen can be a sample of
the whole of the mineral world or an example of a
particular category.
Stalactite: a mineral formation
that develops inside of a cavern over a long period of time
due to mineral-rich water that drips from the ceiling, the
dissolved minerals slowly accumulate into an icicle-like
formation
Stalagmite: a mineral formation
that develops inside of a cavern over a long period of time
due to mineral-rich water that drips from the ceiling onto
the floor, as the minerals collect, crystallize and build
over time the formation resembles a stack or tower
Strontium: a member of the periodic
table of elements (Sr,38) and an alkali earth metal, it is
a soft, silver-white or yellowish, metallic element that is
highly reactive chemically
Sulfate: a salt of sulfuric acid
Sulfide: Most major ores of
important metals such as copper, lead and silver are
sulfides. They are also soft to medium in hardness, opaque,
metallic and igneous in origin. These metallic elements
combine with sulfur (which then acts as a semimetal) to
form sulfides.
Sulfur: a member of the periodic table of
elements (S,16) and an abundant, tasteless, multivalent,
nonmetal and a yellow crystalline solid essential element
for plant and animal life
Syenite: a coarse-grained,
intrusive, igneous rock of the same general composition as
granite but with quartz being absent or present in very
small amounts, mostly orthoclase, alkaline feldspar with
aluminum being an important element
Table of Elements: a tabular method
of displaying the chemical elements, invented in 1869 by
Dmitri Mendeleev to illustrate recurring (periodic ) trends
in properties of the elements, the table has been refined
and even extended over time as new elements have been
discovered and with better understanding of how chemical
elements behave
Tabular Crystals: flat tablet
shaped habit of growth
Tectosilicates: also called
“framework silicates” because their structure is composed
of interconnected tetrahedrons (four faced triangles) going
outward in all directions forming an intricate framework
with their oxygen atoms at each corner, almost 75% of the
Earth’s crust is composed of minerals with this
three-dimensional framework
Tetrahedron: a shape composed of
four triangular faces thereby giving it four points at
which these faces meet
Titanium: a member of the periodic
table of elements (Ti,22) and a light, strong, lustrous,
corrosion-resistant, transition metal with a white-silvery
metallic color which has the highest strength-to-weight
ratio of any metal and is found in almost all living
things, rocks, water bodies, and soils
Titanium Dioxide: a naturally
occurring oxide of titanium which is used as a pigment in
paints
Tourmaline Group: The eleven
members of this group display a large variety of colors,
including red, orange, yellow, green, blue, violet, white,
gray, black and brown. Species of this group crystallize in
the hexagonal system and are usually elongated prisms,
sometimes stubby or with different terminations on each end
of the crystal. Formed in igneous, metamorphic and
sedimentary rock.
Translucent: the ability to see
light through a stone
Transparent: the ability to see clearly
through a stone
Tucson Gem and Mineral Show: The
show is a yearly gathering of gem, fossil and mineral
dealers from around the world held in Tucson Arizona for
two weeks in the month of February. It grows more each year
and vendors cover a vast portion of the city bringing
multiple millions of dollars into the community.
Tungsten: a member of the periodic
table of elements (W,74) and a very hard, heavy, steel-gray
to white transition metal with the highest melting point of
all non-alloyed metals, the second highest of all elements
after carbon and a super alloy with broad applications
Vapor Coating: a technique used to
deposit a thin film one atom (or molecule) at a time onto
the surface of a stone, used on clear stones to give a
colorful rainbow effect
Veins: a long narrow opening or
crack in a rock formation or an ore deposit that fills with
water and minerals and over time crystallizes into another
mineral or crystal formation
Verdelite: green tourmaline in
which its coloring is due to chromium
Vug: a cavity in rock lined with
mineral crystals
Zinc: a member of the periodic
table of elements (Zn,30) and a moderatley-reactive,
bluish-white metal that tarnishes in moist air, when burned
it gives off plumes of zinc oxide
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