adularia  A moderate to low-temperature mineral of the alkali feldspar group: KAlSi3O8.  It is weakly triclinic (formerly regarded as apparently monoclinic) and typically occurs in well-developed, usually transparent, and colorless to milky white (and often opalescent) pseudo-orthorhombic crystals in fissures in crystalline schists, especially in the region of the Swiss Alps.  Adularia displays pearly internal reflections and a fascinating variety of optical behavior between crossed nicols.  It typically has a relatively high content of barium.


albite A common feldspar that is most often associated with the plagioclase series where it is an end member of this series. The plagioclase series comprises feldspars that range in chemical composition from pure NaAlSi3 O8 to pure CaAl2 Si2 O8 . The various plagioclase feldspars are identified from each other by gradations in index of refraction and density in the absence of chemical analysis and/or optical measurements. Albite is also an end member of the alkali or K-feldspars whose series ranges from pure NaAlSi3 O8 to pure KAlSi3 O8. This series only exists at high temperatures with the mineral sanidine being the potassium, K, rich end member. At lower temperatures, the K-feldspars will separate from the albite in a process called exsolution. The albite will form layers inside the k-feldspars crystals. Some times these layers are discernable to the naked eye and the stone is referred to as perthite. Albite by definition must contain no less than 90% sodium and no more than 10% of either potassium and/or calcium in the cation position in the crystal structure.

Albite is the last of the feldspars to crystallize from molten rock. The process of crystallization from a molten rock body serves to isolate rarer elements in the last stages of crystallization and therefore produces rare mineral species. Thus albite is often found with some lovely rare and beautiful minerals. Although usually not an exceptional collection mineral in itself, albite can be a nice accessory mineral to other mineral species. A variety associated with tourmaline is called cleavelandite and forms extremely thin, platy, white and sometimes very transparent crystals.


alkali feldspar (a) A group of feldspars composed of mixtures, or mixed crystals, of potassium feldspar (Or, or KAlSi3O8) and sodium feldspar (Ab, or NaAlSi3O8) in any ratio; a group of feldspars containing alkali metals but little calcium. (b) A mineral of the alkali feldspar group, such as microcline, orthoclase, sanidine, adularia, albite, anorthoclase, and plagioclase in which the proportion of the An molecule is less than 20%.  Synonym: alkalic feldspar.


allanite  A monoclinic, cerium-bearing mineral of the epidote group: (Ce, Ca, Y)(Al, Fe)3(SiO4)3(OH).  It is typically an accessory mineral in igneous rocks (granite, syenite, diorite, pegmatite) and their metamorphic equivalents.  Synonyms: orthite; cerine; bucklandite; treanorite.


apatite  (a) A group of variously colored hexagonal minerals consisting of calcium phosphate together with fluorine, chlorine, hydroxyl, or carbonate in varying amounts and having the general formula: Ca5(PO4, CO3)3(F, OH, Cl).  Also, any mineral of the apatite group, such as fluorapatite, chlorapatite, hydroxylapatite, carbonate-apatite, and francolite; when not specified, the term usually refers to fluorapatite.  The apatite minerals occur as accessory minerals in almost all igneous rocks, in metamorphic rocks, in veins and other ore deposits; and most commonly as fine-grained and often impure masses as the chief constituent of phosphate rock and of most or all bones and teeth.  Synonym: calcium phosphate. (b) A group of hexagonal minerals having the general formula: A5(RO4)3(F, OH, Cl), where A = Ca, SR, or Pb, and R = P, As, V, or less commonly Si.  Examples include svabite, hedyphane, mimetite, pyromorphite, vanadite.


Alpha particle - An alpha particle is a nucleus of a helium atom and is composed of two protons and two neutrons. Because of its charge and relatively large mass, an alpha particle with less than 10 MeV energy has a penetration range of less than one millimeter in tissue.


Becquerel - The becquerel (Bq) is the SI unit for radioactive source activity and is equal to the amount of material that will produce one nuclear decay per second. Note that 1 Bq = 27.027 picoCuries (pCi).


Beta particle - Negative beta particles are electrons and positive beta particles (positrons) are anti-electrons.


biotite (a) A widely distributed and important rock-forming mineral of the mica group: K(Mg, Fe+2)3(Al, Fe+3)Si3O10(OH)2.  It is generally black, dark brown, or dark green, and forms a constituent of crystalline rocks (either as an original crystal in igneous rocks of all kinds or a product of metamorphic origin in gneisses and schists) or a detrital constituent of sandstones and other sedimentary rocks.  Biotite is useful in the potassium-argon method of age determination. (b) A general term to designate all ferromagnesian micas.  Synonyms: black mica; iron mica; magnesia mica.


carnallite  A milk-white to reddish orthorhombic mineral: KMgCl3 6H2O.  It occurs as a saline residue and is a raw material of fertilizer manufacture in some European districts.


chert  Hard massive dense vitreous rock composed principally of silica; as defined by  Woodring, Bramlette, and Kew (1946)


cherty shale  Hard platy dense vitreous rock composed principally of silica; as defined by  Woodring, Bramlette, and Kew (1946)


Crenshaw extension  Refers to an abandoned part of Crenshaw Road that runs along the northern edge of the Portuguese Bend Landslide (refer to the digital version of the map by Conrad and Ehlig (1987)).


Coulomb - The coulomb (C) is the standard unit of electric charge in the International System of Units (SI). It is a dimensionless quantity and is equal to approximately 6.24 x 1018.


Curie - The Curie (Ci) is an older unit for radioactive source decay and is equal to the amount of material that will produce 3.7 x 1010 nuclear decays per second (dps). Because 1 Curie is a large amount of radioactivity, more common units are microCuries (mCi) or picoCuries (pCi).


diatomite  Soft massive or laminated rock containing abundant diatoms; as defined by  Woodring, Bramlette, and Kew (1946)


diatomaceous mudstone  Soft massive rock composed of fine-grained clastic material containing diatoms; as defined by  Woodring, Bramlette, and Kew (1946)


diatomaceous shale  Soft layered or laminated rock composed of fine-grained clastic material containing diatoms; as defined by  Woodring, Bramlette, and Kew (1946)


Dolostone - A sedimentary rock composed primarily of dolomite, a mineral made up of calcium, magnesium, carbon, and oxygen. Dolostone is thought to form when magnesium ions replace some of the calcium ions in limestone, to which dolostone is similar in both appearance and chemical structure.


feldspar (a) A group of abundant rock-forming minerals of general formula: MAl(Si,Al)3O8, where M = K, Na, Ca, Ba, Rb, Sr, and Fe.  Feldspars are the most widespread of any mineral group and constitute 60% of the Earth's crust; they occur as components of all kinds of rocks (crystalline schists, migmatites, gneisses, granites, most magmatic rocks) and as fissure minerals in clefts and druse minerals in cavities.  Feldspars are usually white or nearly white and clear and translucent (they have no color of their own but are frequently colored by impurities), have a hardness of 6 on the Mohs scale, frequently display twinning, exhibit monoclinic or triclinic symmetry, and possess good cleavage in two directions intersecting at 90o as in orthoclase and at about 80o as in plagioclase).  On decomposition, feldspars yield a large part of the clay of soil and also the mineral kaolinite. (b) A mineral of the feldspar group, such as alkali feldspar (orthoclase, microcline), plagioclase (albite, anorthite), and celsian.  Synonyms: feldspar, feldspath.


Gamma ray - Gamma rays are electromagnetic rays produced by the decay of radioactive nuclei.


glauconite  (a) A dull-green earthy or granular mineral of the mica group: (K, Na)(Al, Fe+3, Mg)2(Al, Si)4O10(OH)2.  It has often been regarded as the iron-rich analogue of illite.  Glauconite occurs abundantly in greensand, and seems to be forming in the marine environment at the present time; it is the most common sedimentary (diagenetic) iron silicate and is found in marine sedimentary rocks from the Cambrian to the present.  Glauconite is an indicator of very slow sedimentation.  (b) A name applied to a group of green minerals consisting of hydrous silicates of potassium and iron.


Gray - The gray (Gy) is the SI unit of absorbed radiation dose in terms of the energy actually deposited in the tissue. The gray is defined as 1 joule of deposited energy per kilogram of tissue. Note that 1 Gy = 100 rad.


half-life The length of time required for half of the atoms of a radioactive isotope to decay.


Joule - The joule is a measure of energy and is often expressed in units of newton-meters or watts per second. Note that 1 J = 6.241 x 1018 eV.


Jurassic - The Jurassic is a geologic period that extends from about 135 to 195 million years before the present.


kainite  A usually whitish monoclinic mineral: MgSO4 KCl 3H2O.  It is a natural salt occurring in irregular granular masses, and is used as a source of potassium and magnesium compounds.


keV Abbreviation for thousands of electron volts.


leucite  A white or gray mineral of the feldspathoid group: KAlSi2O6.  It is an important rock-forming mineral in alkalic rocks (esp. lavas), and usually occurs in trapezohedral crystals with a glassy fracture.  Synonyms: amphigene; grenatite; white garnet; Vesuvian garnet; vesuvian.


Maximum likelihood clustering algorithm  This refers to a statistical routine that allows the clustering method to use unequal metrics along the variable axes used to define the clusters. This permits the cluster to occupy an asymmetric volume in the n-dimensional space. Many other methods require a symmetric volume.


Mesozoic - The Mesozoic is a geologic era that extends from approximately 245 million years before the present to about 64 million years. It includes three geologic periods; from oldest to youngest, the Triassic, Jurassic, and Cretaceous. The lower (oldest) boundary is set at the Permian extinction. The upper (youngest) boundary is set at the Cretaceous extinction.


MeV Abbreviation for millions of electron volt.


microcline  A clear, white to gray, brick-red, or green mineral of the alkali feldspar group: KAlSi3O8.  It is the fully ordered, triclinic modification of potassium feldspar and is dimorphous with orthoclase, being stable at lower temperatures; it usually contains some sodium in minor amounts.  Microcline is a common rock-forming mineral of granitic rocks and pegmatites, and is often secondary after orthoclase.  It is generally characterized by cross-hatch twinning.


Miocene Geologic epoch corresponding to 5 - 24 million years before the present.


monazite  A yellow, brown, or reddish-brown monoclinic mineral: (Ce, La, Nd, Th)(PO4, SiO4).  It is a rare-earth phosphate with appreciable substitution of thorium for rare earths and silicon for phosphorous; thorium-free monazite is rare.  It is widely disseminated as an accessory mineral in granites, gneisses, and pegmatites, and it is often naturally concentrated in detrital sand, gravel, and alluvial tin deposits.  Monazite is a principal ore of the rare earths and the main source of thorium.  Synonym: cryptolite.


muscovite  (a) A mineral of the mica group: KAl2(AlSi3)O10(OH)2.  It is colorless to yellowish or pale brown, and is a common mineral in gneisses and schists, in most acid igneous rocks (such as granites and pegmatites), and in many sedimentary rocks (esp. sandstone).  Synonyms: white mica; potash mica; common mica; Muscovy glass; mirror stone.


mybp  Abbreviation for millions of  years before the present.



NaI(Tl) Abbreviation for thallium-activated sodium iodide crystals.


orthoclase  (a) A colorless, white, cream-yellow, flesh pink, or gray mineral of the alkali feldspar group: KAlSi3O8.  It is the partly ordered, monoclinic modification of potassium feldspar and is dimorphous with microcline, being stable at higher temperatures; it usually contains some sodium in minor amounts.  Ordinary or common orthoclase is a common rock-forming mineral; it occurs esp. in granites, acid igneous rocks, and crystalline schists, and is usually perthitic.  Synonyms: common feldspar, orthose, pegmatolite.  (b)  A general term applied to any potassium feldspar that is or appears to be monoclinic; e.g. sanidine, submicroscopically twinned microcline, adularia, submicroscopically twinned analbite.


pCi/L  Abbreviation for picoCuries per liter; 1 picoCurie = 0.037 radioactive decays per second; 1 pCi/L = 37 Bq/m3 (Becquerel per cubic meter)


Planck's constant - Planck's constant is equal to 6.626 x 10-34 Joule-seconds (J sec) and is used to calculate the energy of a photon by multiplying it times the frequency of the photon.


Pliocene Geologic epoch corresponding to 1.6 - 5 million years before the present.


Pleistocene Geologic epoch corresponding to the period from about 10,000 years to 1.6 million years before the present.


porcelaneous mudstone  Hard massive nonlustrous rock composed of silica and fine-grained clastics; as defined by  Woodring, Bramlette, and Kew (1946)


porcelaneous shale  Hard laminated platy nonlustrous rock composed of silica and fine-grained clastics; as defined by  Woodring, Bramlette, and Kew (1946)


ppm  abbreviation for parts per million, a unit of measure for concentration of an element in a sample.


PVPUSD  Acronym for Palos Verdes Peninsula Unified School District.


pyrochlore  (a) A pale-yellow, red, brown, or black isometric mineral: (Na, Ca)2(Nb, Ta)2O6(OH, F).  It is isomorphous with microlite, with Nb greater than Ta, and it usually contains cerium and titanium.  Pyrochlore occurs in pegmatites derived from alkalic igneous rocks and constitutes an ore of niobium.  Synonym: pyrrhite.  (b) An group of minerals of the general formula: A2B2O6(O, OH, F), where A = Na, Ca, K, Fe+2, U+4, Sb+3, Pb, Th, Ce, or Y, and B = Nb, Ta, Ti, Sn, Fe+3, or W.  It includes minerals such as pyrochlore, microlite, betafite, obruchevite, and pandaite.


Quality factor - The radiation quality factor (equivalent to relative biological effectiveness) is a value used to calculated the biologically effective dose for different types of radiation. This is necessary because the different types of radiation cause different amounts of ionization in tissue. For alpha particles the relative biological effectiveness (rbe) may be as high as 20 and for x-rays and gamma rays, the rbe is taken as one.


Quartz - Quartz is one of the most common rock-forming minerals and consists of crystalline silica (SiO2). It occurs either in transparent hexagonal crystals or in crystalline or cryptocrystalline masses. Quartz may be colorless or colored by impurities.


Rad - The rad is a unit of absorbed radiation dose in terms of the energy actually deposited in the tissue. The rad is defined as an absorbed dose of 0.01 joules of energy per kilogram of tissue.


Radiolarian mudstone  Soft massive rock composed of fine-grained clastic material in which Radiolaria are more conspicuous than diatoms; as defined by  Woodring, Bramlette, and Kew (1946)


Rem - The biologically effective dose in rems is the radiation dose in rads multiplied by a "quality factor" which is an assessment of the effectiveness of that particular type and energy of radiation. For alpha particles the relative biological effectiveness (rbe) may be as high as 20, so that one rad is equivalent to 20 rems. However, for x-rays and gamma rays, the rbe is taken as one so that the rad and rem are equivalent for those radiation sources. Note that 1 rem = 0.01 sv.


Roentgen - The roentgen (R) is a measure of radiation intensity of x-rays or gamma rays. It is formally defined as the radiation intensity required to produce an ionization charge of 0.000258 coulombs per kilogram of air. It is one of the standard units for radiation dosimetry, but is not applicable to alpha, beta, or other particle emission and does not accurately predict the tissue effects of gamma rays of extremely high energies.


sanidine  A high-temperature mineral of the alkali feldspar group: KAlSi3O8.  It is a highly disordered monoclinic form, occurring in clear, glassy, often tabular crystals embedded in unaltered acid volcanic rocks such as trachyte; it appears to be stable under equilibrium conditions above approximately 500o C.  Sanidine forms a complete solid-solution series with high albite, and some sodium is always present.  Synonyms: glassy feldspar, ice spar, rhyacolite.


sericite  A white, fine-grained potassium mica occurring in small scales and flakes as an alteration product of various aluminosilicate minerals, having a silky luster, and found in various metamorphic rocks (esp. in schists and phyllites) or in the wall rocks, fault gouge, and vein fillings of many ore deposits.  It is usually muscovite or very close to muscovite in composition, and may also include much illite.


Sievert - The sievert (sv) is the SI unit for effective dose and is calculated by multiplying the radiation dose in grays by the radiation quality factor.


Speed of light - The speed of light is equal to approximately 2.99792 x 108 meters per second.


sphene  A usually yellow or brown mineral: CaTiSiO5.  It often contains other elements such as niobium, chromium, fluorine, sodium, iron, manganese, and yttrium.  Sphene occurs in wedge-shaped or lozenge-shaped monoclinic crystals as an accessory mineral in granitic rocks and in calcium-rich metamorphic rocks.  Synonyms: titanite, grothite.


sylvite  A white or colorless isometric mineral: KCl.  It is the principal ore mineral of potassium compounds.  Sylvite occurs in beds as a saline residue with halite and other evaporites.  It has a sharper taste than that of halite.  Synonyms: sylvine; leopoldite.


thorite  A brown, black, or sometimes orange-yellow tetragonal mineral: ThSiO4.  It is isostructural with thorogummite, strongly radioactive, and usually metamict, and may contain as much as 10% uranium.  Thorite resembles zircon and occurs as a minor accessory mineral of granites, syenites, and pegmatites.  It is dimorphous with huttonite.


uraninite  A black, brown, or steel-gray octahedral or cubic mineral, essentially UO2, but usually partly oxidized.  It is strongly radioactive, and is the chief ore of uranium.  It is isomorphous with thorianite.  Uraninite often contains impurities such as thorium, radium, the cerium and yttrium metals, and lead; when heated, it yields a gas consisting chiefly of helium.  It occurs in veins of lead, tin, and copper minerals and in sandstone deposits, and is a primary constituent of granites and pegmatites.  Synonyms: ulrichite; coracite.


xenotime  A brown, yellow or reddish tetragonal mineral: YPO4.  It is isostructural with zircon, and often contains erbium, cerium, and other rare earths, as well as thorium, uranium, aluminum, calcium, beryllium, zirconium, or other elements.  Xenotime occurs as an accessory mineral in granites and pegmatites.


X-ray - X-rays are electromagnetic rays produced by high-energy atomic transitions. X-rays have wavelengths between approximately .01 nanometers to 200 nanometers (corresponding to about 6-125 keV ).


zircon  A mineral ZrSiO4.  It occurs in tetragonal prisms, has various colors, and is a common accessory mineral in siliceous igneous rocks, crystalline limestones, schists, and gneisses, in sedimentary rocks derived therefrom, and in beach and river placer deposits.  It is the chief ore of zirconium, and is used as a refractory; when cut and polished, the colorless varieties provide exceptionally brilliant gemstones.  Synonyms: zirconite, hyacinth, jacinth.

























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