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THIS SECTION IS UNDER DEVELOPMENT
- Accidental Inclusion
Enclosed rocks or crystals having no genetic connectionwith the igneous rock in which they are found. Also see Xenolith.
- Acicular
Needle-like in form.
- Acicular Microlite
A hairlike or very thin microlite. Often occurs in dense swarms.
- Acicular Trichite
A hairlike or very thin trichite.
- Apache Tear
Rounded obsidian masses found associated with deposits of perlite. Also see marakenite.
- Ashflow Tuff
Ashflow deposit indurated by compaction and heat.
- Asteroidal Trichites
Spiderlike arrangements of trichites radiating from a central point.
- Basalt
Extrudive volcanic rock with an SiO2 content ranging from about 45 percent to 53 percent.
- Belonite
An elongated or acicular crystallite having rounded or pointed ends.
- Biface
Artifact with contiguous flakes scares on both surfaces.
- Breccia
Fragmented rock whose components are angular.
- Calc-Alkaline
- Caldera
Large basin-shaped volcanic depression roughly circular in form.
- Characterization
The use of a distinguishing attribute or characteristic to identify a specific source.
- Chemical Source
- Chemical Source
See Selvage
- Conchoidal Fracture
Smoothly-curved fracture surface that is typical of obsidian or quartz.
- Crystallite
A broad term applied to a minute body of unknown mineralologic composition or crystal form which does not polarize light.
- Dacite
Volcanic rock with an SiO2 content ranging from about 63 percent to 70 percent.
- Dendrochronologic Calibration
- Devitrification
- Diffusion Front
See Hydration Rim Diffusion Front.
- Erratics
See Glacial Erratics.
- Eutectic Point
- Felsic
- Felsite
- Float
Surface rocks or nodules found separated from parent veins of strata.
- Fluvial
Pertainign to river or stream activity.
- Geochemical Source
- Glacial Erratics
Ice-transported rocks.
- Globulite
- Groundmass
- Holohyaline
An igneous rock composed entirely of glass.
- Hydration Rate
- Hydration Rim
- Hydration Rim Diffusion Front
- Ignimbrite
- Index of Refraction
- INAA
Instrumental neutron activation analysis.
- Isotropic
Exhibiting the same optical properties (when viewed under polarized light) in all orientations.
- K-Ar
See Potassium-Argon Age.
- Lahar
- Lath
Long, thin crystal.
- Lithoidal
Term applied to devitrified glass.
- Lithophysae
- Longulite
- Mafic
- Major Elements
Element occurring in abundance greater than about 0.1 percennt (1000 ppm).
- Margarite
- Marakenite
Rounded obsidian masses found associated with deposits of perlite. Also see Apache Tear.
- Microlite
- Microlith
A microlite.
- Micron
One-millionth of a meter. Standard unit used to measure obsidian hydration rims.
- Microphenocryst
- Minor Element
- NAA
Neutron activation analysis.
- Obsidian Hydration Years
- Obsidian-Like Vitrophyre
- Peralkaline
- Perlite
- Perlitic Texture
- Petrography
Branch of geology dealing with the description and classification of rocks.
- Phenocryst
A relatively large crystal set in a finer-grained or glassy groundmass.
- Porphyritic
Textural term for igneous rocks ni which larger crystals are set in a finer groundmass that may be crystalline or glassy.
- Potassium-Argon Age
- ppm
Parts per million.
- Primary Source
- Prismatic Microlite
Rod-shaped microlite.
- Provenance
- Provenancing
- Provenience
- Pyroclastic
- Radiocarbon Years
- Rhyodacite
- Rhyolite
- Scopulite
- Secondary Source
- Selvage
- Source
- Spherulite
- Tachylyte
- Thin Section
- Trace Element
Element occurring in abundance less than about 0.1 percent (1000 ppm).
- Trachytic
- Trichite
- Tuff
- Vent
- Vitreous
- Vitrophyre
- Welded Ashflow
- Welded Tuff
- XRF
X-ray fluorescence (an analytical method used to determine the chemical composition of rocks).
- Xenolith
A rock fragment foriegn to the body of igneous rock in which it is found. Also see Accidental Inclusion.
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