Essential Minerals |
Potash Feldspar > 2/3 Total Feldspar | ||||
Quartz > 10% | Quartz < 10% Feldspathoid < 10% |
Feldspathoid > 10% | |||
Characterizing Accessory Minerals |
Chiefly: Hornblende, Biotite, Pyroxene, Muscovite Also: Sodic Amphiboles, Aegirine, Cancrinite, Sodalite, Tourmaline |
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Color Index | 10 | 15 | 20 | ||
Average Chemical Composition (DALY) |
SiO2 | 71.5 | 60.4 | 56.0 | |
Al2O3 | 14.0 | 17.0 | 19.2 | ||
Fe2O3 | 1.5 | 2.7 | 2.9 | ||
FeO | 1.4 | 2.9 | 1.6 | ||
MgO | 0.6 | 1.8 | 0.6 | ||
CaO | 1.6 | 3.7 | 2.0 | ||
Na2O | 3.4 | 4.2 | 8.5 | ||
K2O | 4.3 | 5.1 | 5.3 | ||
Phaneritic | Equigranular Batholiths, lopoliths, stocks, large laccoliths, thick dikes, and sills |
Granite |
Syenite QUARTZ SYENITE: a little quartz ALKALI SYENITE: no plagioclase except albite PULASKITE: a little nepheline NORDMARKITE: a little quartz LARVIKITE: with "blue" feldspar SHONKINITE: abundant FeMg minerals |
Nepheline Syenite LEUCITE SYENITE: pseudoleucite only feldspathoid SODALITE SYENITE: sodalite only feldspathoid FOYAITE: abundant feldspar MALIGNITE: abundant FeMg minerals DITROITE: with nepheline and sodalite |
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Porphyritic | Phaneritic Groundmass Laccoliths, dikes, sills, plugs, small stocks, margins of larger masses |
Granite Porphyry | Syenite Porphyry | Nepheline Syenite Porphyry | |
Aphanitic Groundmass Dikes, sills, laccoliths, surface flows, margins of larger masses, welded tuffs |
Rhyolite Porphyry | Trachyte Porphyry | Phonolite Porphyry | ||
Aphanitic | Microcrystalline Dikes, sills, surface flows, margins of larger masses, welded tuffs |
Rhyolite | Trachyte | Phonolite LEUCITE PHONOLITE: (Leucite trachyte) leucite only feldspathoid TINGUAITE: abundant aegirine WYOMINGITE: leucite and phlogopite |
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Glassy |
Obsidian: black Pitchstone: resinous Vitrophyre: porphyritic Perlite: concentric fractures Pumice: finely cellular, light colored Scoria: coarsely cellular, dark colored |
Normally it is not possible to determine the composition of these rocks. They are customarily designated by the names at the left of this column. Basic glass is rare so rocks named, except scoria, will normally be silicic. If the approximate composition (by close association) or silica content (by refractive index or analysis), can be determined, the name may be prefixed by the name of the appropriate aphanitic rock, for example, "trachyte obsidian," or "latite vitrophyre." In general, scoria is basic; basic obsidian is called "tachylite"; and spherulitic tachylite is "variolite." |
Essential Minerals |
Potash Feldspar 1/3 - 2/3 Total Feldspar | ||||
Quartz > 10% | Quartz < 10% Feldspathoid < 10% |
Feldspathoid > 10% |
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Characterizing Accessory Minerals |
Chiefly: Hornblende, Biotite, Pyroxene Also: Sodic Amphiboles, Aegirine |
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Color Index | 20 | 25 | 30 | ||
Average Chemical Composition (DALY) |
SiO2 | 66.8 | 57.0 | 54.1 | |
Al2O3 | 15.8 | 17.1 | 21.0 | ||
Fe2O3 | 2.3 | 3.4 | 1.8 | ||
FeO | 1.3 | 3.6 | 3.3 | ||
MgO | 1.0 | 2.3 | 1.1 | ||
CaO | 2.8 | 5.4 | 3.2 | ||
Na2O | 3.7 | 4.7 | 6.2 | ||
K2O | 4.2 | 3.7 | 5.9 | ||
Phaneritic | Equigranular Batholiths, lopoliths, stocks, large laccoliths, thick dikes, and sills |
Quartz Monzonite (ADAMELLITE) |
Monzonite | Nepheline Monzonite | |
Porphyritic | Phaneritic Groundmass Laccoliths, dikes, sills, plugs, small stocks, margins of larger masses |
Quartz Monzonite Porphyry | Monzonite Porphyry | Nepheline Monzonite Porphyry | |
Aphanitic Groundmass Dikes, sills, laccoliths, surface flows, margins of larger masses, welded tuffs |
Quartz Latite Porphyry | Latite Porphyry | Nepheline Latite Porphyry | ||
Aphanitic | Microcrystalline Dikes, sills, surface flows, margins of larger masses, welded tuffs |
Quartz Latite (DELLENITE) |
Latite (TRACHY-ANDESITE) |
Nepheline Latite | |
Glassy |
Obsidian: black Pitchstone: resinous Vitrophyre: porphyritic Perlite: concentric fractures Pumice: finely cellular, light colored Scoria: coarsely cellular, dark colored |
Normally it is not possible to determine the composition of these rocks. They are customarily designated by the names at the left of this column. Basic glass is rare so rocks named, except scoria, will normally be silicic. If the approximate composition (by close association) or silica content (by refractive index or analysis), can be determined, the name may be prefixed by the name of the appropriate aphanitic rock, for example, "trachyte obsidian," or "latite vitrophyre." In general, scoria is basic; basic obsidian is called "tachylite"; and spherulitic tachylite is "variolite." |
Essential Minerals |
Plagioclase Feldspar > 2/3 Total Feldspar | |||||||
Potash Feldspar > 10% Total Feldspar | Potash Feldspar < 10% Total Feldspar | |||||||
Sodic Plagioclase | Calcic Plagioclase | |||||||
Quartz > 10% | Quartz > 10% | Quartz < 10% Feldspathoid < 10% |
Quartz < 10% Feldspathoid < 10% |
Feldspathoid > 10% Pyroxene > 10% |
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Characterizing Accessory Minerals |
Chiefly: Hornblende, Biotite, Pyroxene (in Andesite) Also: Pyroxene, Feldspathoid, Sodic Amphiboles |
Chiefly: Pyroxene, Uralite, Olivine Also: Hornblende, Biotite, Quartz, Analcite, Aegirine, Sodic Amphiboles |
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Color Index | 20 | 20 | 25 | 50 | 60 | |||
Average Chemical Composition (DALY) |
SiO2 | 65.3 | 61.6 | 58.2 | 48.6 | 47.4 | ||
Al2O3 | 16.1 | 16.2 | 17.0 | 16.8 | 15.4 | |||
Fe2O3 | 2.1 | 2.5 | 3.2 | 4.8 | 4.9 | |||
FeO | 2.3 | 3.8 | 3.7 | 6.0 | 5.4 | |||
MgO | 1.7 | 2.8 | 3.5 | 5.1 | 5.0 | |||
CaO | 3.9 | 5.4 | 6.3 | 8.9 | 9.7 | |||
Na2O | 3.8 | 3.4 | 3.5 | 3.7 | 3.8 | |||
K2O | 2.7 | 2.1 | 2.1 | 1.9 | 3.5 | |||
Phaneritic | Equigranular Batholiths, lopoliths, stocks, large laccoliths, thick dikes, and sills |
Granodiorite | Quartz Diorite (TONALITE) |
Diorite |
Gabbro |
Diabase (Dolerite of British) Phaneritic diabasic texture, normally medium or fine grained |
Theralite (ESSEXITE, NEPHELINE GABBRO) TESCHENITE: analcite only feldspathoid OLIVINE THERALITE: with olivine |
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Porphyritic | Phaneritic Groundmass Laccoliths, dikes, sills, plugs, small stocks, margins of larger masses |
Granodiorite Porphyry | Quartz Diorite Porphyry | Diorite Porphyry | Gabbro Porphyry | Theralite Porphyry | ||
Aphanitic Groundmass Dikes, sills, laccoliths, surface flows, margins of larger masses, welded tuffs |
Dacite Porphyry |
Andesite |
Basalt Porphyry | Tephrite Porphyry | ||||
Aphanitic | Microcrystalline Dikes, sills, surface flows, margins of larger masses, welded tuffs |
Dacite | Andesite | Basalt OLIVINE BASALT: with olivine ANALCITE BASALT: with analcite QUARTZ BASALT: with quartz OCEANITE: with abundant olivine |
Tephrite LEUCITE TEPHRITE: leucite only feldspathoid BASANITE: with olivine LEUCITE BASANITE: with olivine and leucite |
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Glassy |
Obsidian: black Pitchstone: resinous Vitrophyre: porphyritic Perlite: concentric fractures Pumice: finely cellular, light colored Scoria: coarsely cellular, dark colored |
Normally it is not possible to determine the composition of these rocks. They are customarily designated by the names at the left of this column. Basic glass is rare so rocks named, except scoria, will normally be silicic. If the approximate composition (by close association) or silica content (by refractive index or analysis), can be determined, the name may be prefixed by the name of the appropriate aphanitic rock, for example, "trachyte obsidian," or "latite vitrophyre." In general, scoria is basic; basic obsidian is called "tachylite"; and spherulitic tachylite is "variolite." |
Essential Minerals |
Little or No Feldspar | Special Types | |||
Chiefly Pyroxene and/or Olivine | Chiefly Ferro-Magnesian Minerals and Feldspathoids | ||||
Characterizing Accessory Minerals |
Chiefly: Serpentine, Iron Ore Also: Hornblende, Biotite |
Hornblende, Biotite, Iron Ore | |||
Color Index | 95 | 55 | |||
Average Chemical Composition (DALY) |
SiO2 | 41.1 | 42.0 | ||
Al2O3 | 4.8 | 17.9 | |||
Fe2O3 | 4.0 | 5.7 | |||
FeO | 7.1 | 5.7 | |||
MgO | 32.2 | 3.4 | |||
CaO | 4.4 | 10.3 | |||
Na2O | 0.5 | 8.0 | |||
K2O | 1.0 | 2.4 | |||
Phaneritic | Equigranular Batholiths, lopoliths, stocks, large laccoliths, thick dikes, and sills |
Peridotite |
MISSOURITE: pyroxene, olivine, and pseudoleucite IJOLITE: pyroxene and nepheline FERGUSITE: pyroxene and pseudoleucite UNCOMPAHGRITE (MELILITE PYROXENITE): pyroxene and melilite |
Pegmatite: Aplite: Lamprophyre: |
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Porphyritic | Phaneritic Groundmass Laccoliths, dikes, sills, plugs, small stocks, margins of larger masses |
Peridotite porphyry KIMBERLITE: peridotite porphyry or breccia |
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Aphanitic Groundmass Dikes, sills, laccoliths, surface flows, margins of larger masses, welded tuffs |
Limburgite porphyry |
Trap: Felsite: |
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Aphanitic | Microcrystalline Dikes, sills, surface flows, margins of larger masses, welded tuffs |
Limburgite | NEPHELINITE: pyroxene and nepheline LEUCITITE: pyroxene and leucite MELILITITE: pyroxene and melilite OLIVINE NEPHELINITE (NEPHELINE BASALT): pyroxene, nepheline, and olivine ETC. |
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Glassy |
Obsidian: black Pitchstone: resinous Vitrophyre: porphyritic Perlite: concentric fractures Pumice: finely cellular, light colored Scoria: coarsely cellular, dark colored |
Normally it is not possible to determine the composition of these rocks. They are customarily designated by the names at the left of this column. Basic glass is rare so rocks named, except scoria, will normally be silicic. If the approximate composition (by close association) or silica content (by refractive index or analysis), can be determined, the name may be prefixed by the name of the appropriate aphanitic rock, for example, "trachyte obsidian," or "latite vitrophyre." In general, scoria is basic; basic obsidian is called "tachylite"; and spherulitic tachylite is "variolite." |