| Id | Identification Type | Name | Description | Distinguishing Features | Tags |
|---|---|---|---|---|---|
| 107 | Mineral | Albite | Clear to pale yellow. Nonpleochroic. Low birefringence. Euhedral laths possible in volcanic settings, generally subrounded/subangular in shape. High relief. Can be distinguished from quartz by its 90 degree cleavage. Polysynthetic (albitic, simple) twinning is diagnostic. Sodium endmember of plagioclase solid solution series.
See also feldspar. "Elongate prisms in multiple domains" -Smoot |
polysynthetic-twinning | feldspar silicate plagioclase |
| 21 | Mineral | Amphibole | Transparent colorless to green, brown, red, yellow, depending on mineralogy within the amphibole group. Strongly pleochroic. Moderate birefringence may be masked by color. Anhedral to euhedral prismatic grains. High relief. Hornblende-series minerals the most common detrital amphiboles. | Pleochroic
Subhedral Prismatic |
ferromagnesian high-relief green silicate transparent green |
| 62 | Mineral | Apatite | Usually transparent colorless. Nonpleochroic. Weak birefringence (white-gray). Prismatic, six-sided crystals may be euhedral or subhedral. Moderate relief. May occur as either detrital grains (derived from felsic igneous rocks) or authigenic/diagenetic crystals in phosphate-rich environments. | Prismatic
Moderate-relief Colorless Transparent |
low-birefringence anisotropic euhedral phosphate heavy-mineral |
| 37 | Mineral | Aragonite | Transparent colorless. Nonpleochroic. Extreme birefringence. Distinguished by small (~10 um) acicular (needle-like) or rice-like grain morphology. Moderate relief, varying by direction. Twinning may be common.
Organisms such as pteropods, most mollusks, and some corals produce biogenic aragonite. |
Rice-shape
Acicular Elongate High-birefringence |
Carbonate salt transparent colorless |
| 180 | Contaminant | Backer rod | contaminant | ||
| 175 | Lithofacies | Banded carbonate mud | Lithofacies comprising >50% carbonate minerals, repetitively banded on centimeter scale with more and less organic-rich compositions.
Centimeter to decimeter darker and lighter banding of dominantly calcareous lithology. |
banded calcareous organic-matter |
|
| 186 | Mineral | Barite | Recognized rarely as a diagenetic phase in minerotrophic peatland settings, where it occurs as colorless, prismatic or tabular euhedra with moderate relief and low birefringence. Also may occur in saline lake settings as an evaporite phase. | low-birefringence
low-to-moderate relief prismatic |
prismatic elongated moderate-relief low-birefringence diagenetic |
| 22 | Mineral | Biotite | Occurs as flakes larger than surrounding material, green to brown transparent, may be pleochroic. Low to moderate relief. Cleavage planes frequently visible as platy layers. Classic bird's eye extinction (mottled, pebbly texture) not always present in smear slide. Very low apparent birefringence (pseudo-isotropy) because flakes settle with {001} in the plane of the slide. However, by tilting the slide very slightly (e.g., by slipping another slide under the slide) one can evaluate the true birefringence (thanks to Frank Brown, U. Utah, for the tip). Biotite has strong birefringence; chlorite, which may form as an alteration product or a metamorphic mineral, can look similar to biotite in plane light but has weak birefringence. | Flaky
Pseudo-isotropic Pleochroic bird's-eye-extinction |
brown green layers ragged silicate mica transparent |
| 117 | Contaminant | Bubble | Transparent colorless with heavy black outline. Nonpleochroic, isotropic. Bubbles in optical cement are typically circular but can be any shape when filling voids in biological remains. Very high relief, and may be out of plane of focus of other materials due to larger size. May occur in any slide. Can be partially avoided by keeping bottle of mounting medium upside down when not in use, and mounting several slides at a time so that bubbles are only present in first one or two. | High-relief
spherical |
circular dark high-relief transparent contaminant |
| 115 | Lithofacies | Calcareous silt | Lithofacies comprising >50% detrital mineral material in the silt size range (4-63 microns), with calcium carbonate the most abundant secondary component.
Carbonate grains prominent but secondary; biogenic components variable but subordinate; mineral composition of detrital component depends on erosional sources and their lithologies. |
silty calcareous fine-grained |
|
| 38 | Mineral | Calcite | Transparent colorless to pale greenish. High birefringence. Rhombic or ellipsoidal euhedra, corroded grains, micritic masses most common; more rarely twins, bow-ties, dendrites, sprays. Medium relief. Occurs as inorganic precipitate in lakes, in surface water and diagenetically (including as a replacement); also irregular detrital grains and rock fragments.
Organisms with calcite skeletal components include ostracodes, some molluscs, foraminifera, coccoliths, calcareous nannoplankton, Phacotus, charophytes, peloids, microbialites. |
High-birefringence
Transparent |
carbonate Colorless Rhombic euhedral salt |
| 23 | Mineral | Chlorite | Colorless to yellow or green, transparent, generally pleochroic. Low to moderate relief. Cleavage planes frequently visible as platy layers. Very low apparent birefringence (pseudo-isotropy) because flakes settle with {001} in the plane of the slide. However, by tilting the slide very slightly (e.g., by slipping another slide under the slide) one can evaluate the true birefringence (thanks to Frank Brown, U. Utah, for the tip). Chlorite has weak birefringence and can have anomalous (purplish or brown) interference colors due to its varying chemistry. Occurs as flakes larger than surrounding material when primary, can be fibrous or granular when replacing other minerals. | Flaky
Pseudo-isotropic |
yellow green layers ragged silicate mica transparent low-birefringence |
| 144 | Contaminant | Cigarette Ash | contaminant | ||
| 16 | Mineral | Clay | |||
| 170 | Lithofacies | Clay turbidite cap | Describes the finest, suspended component of a subaqueous density-flow deposit, settled out of the water column at the end of a transport event.
Position above fining-upward sequence; grain size may be in fine silt or clay range. |
sorted fine-grained graded |
|
| 51 | Mineral | Clinoptilolite | Associated with devitrified volcanic glass. | ||
| 29 | Mineral | Clinopyroxene | Transparent colorless to green or brown. May be pleochroic from yellow to green, depending on mineralogy. Moderate birefringence. Appear as stubby prisms and subhedral to anhedral crystals. Near-90 degree perfect cleavage. Moderately high relief. | Subhedral
near-90-degree-perfect-cleavage |
ferromagnesian silicate transparent green brown pleochroic moderately-high-relief |
| 169 | Lithofacies | Diatom ooze | Lithofacies comprising >50% diatom frustules, with secondary contributions of detrital and/or chemically precipitated material.
High proportion of diatom frustules; intervals deposited during 'blooms' may be nearly pure diatoms, with cheesy or clotted surface texture. Carbonate minerals subordinate, or absent. |
isotropic clotted |
|
| 114 | Lithofacies | Diatomaceous carbonate mud | Describes a lithofacies composed of >50% authigenic carbonate minerals, with diatom frustules as the second-most abundant component.
Diatom frustules prominent but secondary to carbonate minerals; organic matter (amorphous or fragmentary) variable, subordinate; clastic mineral matter subordinate, may be absent. |
high-birefringence calcareous authigenic biogenic |
|
| 39 | Mineral | Dolomite | Transparent colorless. Nonpleochroic. Extremely high birefringence. Equant cleavage rhombs, usually with sharp edges. High relief. Usually detrital but may be authigenic in some rare environments. Usually small (fine silt to clay) grains. Higher relief than calcite, and rhombs generally more equant than calcite, but can be difficult to conclusively distinguish from calcite. | Rhombic
High-birefringence |
carbonate cleavage high-relief equant transparent colorless salt |
| 184 | Mineral | Erionite | Erionite refers to a class of fibrous zeolite minerals with varying Na/Ca/K compositions, typically forming through alteration of volcanic ash or volcaniclasitc sediments. Occurs as void ingrowths and intergranular cement. Its fibrous habit makes erionite a potential inhalation hazard; the mineral is classified as a Group 1 Carcinogen by the International Agency for Research on Cancer. | fibrous
radial low-birefringence |
zeolite fibrous acicular |
| 104 | Mineral | Fecal pellet | |||
| 68 | Mineral | Feldspar | Transparent colorless to cloudy. Nonpleochroic. Low order birefringence. Tabular to prismatic. Relief varies by composition.
"Feldspar" includes several minerals or groups of minerals with solid solutions. According to Rothwell (1989, p.77) the distinguishing features of feldspars are "Subhedral prismatic to tabular form, turbidity due to incipient alteration, distinctive twinning (seen in cross-polars) ... Low birefringence." Alkali feldspars tend to display simple Carlsbad twinning, though Carlsbad twinning can be found in all feldspars (Rothwell, 1989, p.74). Grid (cross-hatched polysynthetic) twinning in two directions is a diagnostic characteristic of microcline, and lamellar (multiple) twinning occurs mainly in plagioclase (Rothwell, 1989, p.74). The width of lamellae in plagioclase relates to composition, with more narrow lamellae in oligoclase and wider lamellae in albite and anorthite (Rothwell, 1989, p.75). More quantitative distinction between plagioclase feldspar minerals of individual mineral grains can be achieved using the Michel-Levy method, which is based on the maximum extinction angles of twin lamellae (Rothwell, 1989, p.71-73). Refer to Rothwell (1989) p.71-73 for a step-by-step description of the Michel-Levy method. Some identifiable feldspars are listed separately in TMI: albite, microcline, and orthoclase. |
good-cleavage
low-birefringence |
feldspar silicate twinned transparent translucent |
| 124 | Contaminant | Fiber | contaminant | ||
| 145 | Contaminant | Floral Foam | contaminant | ||
| 33 | Mineral | Garnet | Transparent colorless to rose or amber. Isotropic. Very high relief. Equant rounded grains are most common, but may also occur as etched and irregular grains. Cleavage absent. Occurs as smaller grains than other minerals in slide because of garnet's higher density. | Isotropic
Heavy-mineral |
pink brown silicate |
| 174 | Lithofacies | Glacial varves | Lithofacies comprising annually laminated sequences of sand, silt or clay deposited in a glacially-influenced lacustrine (or marine) setting.
Repetitively laminated variations in grain size from sand to clay, representing seasonal variations in glacial melt-water cycles and sediment transport; dropstones may be present if deposited in an ice-contact setting. |
laminated graded rythmite glacial |
|
| 15 | Mineral | Glauconite | Blue green to olive green. Often occurs as sand-sized, rounded pellets. Secondary mineral. | green
|
|
| 159 | Mineral | Greigite | Occurs in microbial biofilms, as disseminated crystallites, and as framboids. Opaque where visible by light microscopy. In reduced sediments, greigite is often considered a metastable phase transitional between highly reactive iron monosulfide (mackinawite) and pyrite. Common in reduced lacustrine sediments. | ||
| 46 | Mineral | Gypsum | Transparent colorless. Nonpleochroic. Low birefringence (about the same as quartz). May occur as thin plates (folia), tabular euhedra, or acicular needles. Low relief. Detrital or authigenic. Frequently associated with pyrite when authigenic. May be twinned. Caution: common precipitate from pore waters of cores as they age in storage. Also, heating slide may cause polysynthetic twinning. | Low-relief
Low-birefringence Tabular Acicular |
|
| 143 | Contaminant | Hair | contaminant | ||
| 183 | Mineral | Hematite | see also Iron (Hydr)oxides, Non-opaque (Hematite/Limonite) | ||
| 135 | Mineral | Inclusion | Distinct mineral or fluid phases incorporated within the crystalline structure of a surrounding host mineral grain, often the result of elemental incompatibilities in igneous or metamorphic processes. In smear slides, typically recognized as optically distinct minerals with different birefringence, optical extinction angles, and/or relief from a surrounding, optically unitary, mineral grain. | ||
| 14 | Mineral | Iron (Hydr)oxides, Non-opaque (Hematite/Limonite) | Non-opaque iron oxides, hydroxides, and oxyhydroxides including hematite (which may also occur as opaque grains) and limonite (actually a mixture of minerals including goethite). Red to brown; limonite yellower. High relief. May occur as granular aggregates, scales, either translucent or transparent. May be isotropic or show low-order birefringence.
Hematite is red to brown, transparent to opaque. Red-brown in reflected light. Hematite has high birefringence, but may not be observable due to deep color of grains. Some hematite grains may be noncrystalline and thus isotropic. Irregularly shaped flakes and earthy or somewhat fibrous particles. High relief. Hematite occurs as detrital or authigenic/diagenetic grains. |
Translucent
Transparent Granular |
red brown yellow |
| 6 | Mineral | Iron Oxides, Opaque (e.g., magnetite) | Fully opaque where visible by light microscopy. In coarser, sorted lacustrine sediment, cubic, faceted, or irregularly blocky grains may occur in association with other high-density minerals. May be distinguished from pyrite and other sulfides by grey color under oblique reflected light. Biomineralized magnetite produced by magnetotactic bacteria is widespread in sedimentary environments, but normally in a sub-micron size class well below that of grains discerned in smear slides. | heavy-mineral | |
| 146 | Contaminant | Kimwipe | contaminant | ||
| 147 | Contaminant | Lab Dust | contaminant | ||
| 168 | Lithofacies | Laminated sulfidic silt | Describes a lithofacies comprising finely structured clastic sediment with prominent accessory sulfide minerals, especially fine reactive monosulfide (mackinawite).
Distinguished by fine-scale bedding and abundance of opaque minerals; often highly pungent when freshly exposed. |
fine-scale-bedding
pungent |
opaque black pungent reactive diatomaceous |
| 132 | Mineral | Lithic fragment | Wide variety of forms and optical properties. A very small rock made up of one or more minerals. Can be identified by the presence of grain boundaries within a particle. | grain-boundaries | |
| 102 | Mineral | Magadiite | Rare evaporite mineral common to Lake Magadi, Kenya. | silicate evaporite transparent colorless |
|
| 55 | Mineral | Microcline | Transparent colorless. Nonpleochroic. Low order birefringence colors. Distinctive twinning pattern from the intersection of pericline and albitic twins ("tartan plaid" or "cross-hatched") in cross-polarized light is virtually diagnostic of microcline. Tabular and cleavage fragments. Moderate relief.
See also feldspar. |
tartan-twinned
low-birefringence |
silicate plaid tartan cross-hatch twinned feldspar cleavage transparent colorless |
| 7 | Mineral | Micronodule | |||
| 148 | Contaminant | Mold | contaminant | ||
| 48 | Mineral | Muscovite | Transparent, colorless. Strong second-order birefringence. Shredded or stringy texture common. Low relief. Usually does not look similar to biotite. | Shredded
Stringy Colorless High-birefringence |
ragged transparent mica silicate |
| 40 | Mineral | Olivine | Transparent colorless to pale gray-green. Nonpleochroic. Vivid birefringence colors. Frequently occurs as subangular anhedral grains. Conchoidal fracture. Moderately high relief. Associated with calcic plagioclase and pyroxene. | Conchoidal-fracture
Moderately-high-relief Anhedral |
silicate ferromagnesian transparent colorless gray |
| 103 | Mineral | Opal | |||
| 116 | Lithofacies | Organic-rich carbonate mud with pyrite | Refers to a lithofacies comprising >50% chemically precipitated carbonate minerals, abundant secondary organic matter, and prominent accessory pyrite.
Prominent co-occurrence of carbonate and opaque minerals. Likely to be pungent (H2S). |
opaque black high-birefringence pungent stinky |
|
| 163 | Lithofacies | Organic-rich Diatom Ooze | Refers to a lithofacies comprising >50% diatom frustules, with organic matter (amorphous and/or fragmentary) making up the second-most abundant constituent.
Prominence of diatom frustules; diatoms may be diverse, or essentially monospecific. Carbonate minerals subordinate, or absent. Clastic silt subordinate, or absent. Diagenetic minerals (e.g., vivianite; pyrite) occur commonly, but are subordinate. |
circular transparent colorless rice-shape brown amorphous |
|
| 53 | Mineral | Orthoclase | Colorless to pale yellow, nonpleochroic, low birefringence, commonly elongate when euhedral, moderate to high relief, contact twinning is virtually diagnostic (only one twin plane in a single crystal).
See also feldspar. |
no-lamellar-twinning
contact-twinning |
feldspar silicate |
| 28 | Mineral | Orthopyroxene | Transparent colorless to green or brown. May be pleochroic from pale red to greenish (hypersthene). Low birefringence. Appear as stubby prisms and subhedral to anhedral crystals. Near-90 degree perfect cleavage. Moderately high relief. | Subhedral | Ferromagnesian pleochroic silicate transparent brown green good-cleavage moderately-high-relief |
| 13 | Mineral | Palagonite | Yellow or yellowish brown, amorphous to weakly birefringent, heterogeneous material forming through low-temperature hydration and elemental alteration of basaltic volcanic glass. Further alteration of palagonite produces zeolite minerals and smectite clays.
Palagonitized grains may retain glass shard forms. Association with unaltered volcanic glass and other volcanigenic sediment components such as pyroxenes and plagioclase feldspar. |
||
| 164 | Lithofacies | Peat | Lithofacies referring to a sediment consisting of >80% authigenically produced organic matter.
High proportion of organic matter to mineral grains. Organic material may be coarsely fragmentary, or degraded. |
organic-matter fibrous fragmentary bryophyte woody |
|
| 52 | Mineral | Phillipsite | Prismatic, very often as cruciform (cross-shaped) twins or rosettes, colorless with low-moderate relief and low-order birefringence. Phillipsite is a zeolite-family mineral typically formed through alteration of mafic volcanic rocks or tephras, and may be found in association with other zeolites, especially in saline lake or marine sediments. | zeolite | |
| 111 | Mineral | Pirssonite | Colorless, prismatic or tabular, with high-order birefringence and moderate relief. Pirssonite is a hydrous Mg-Ca carbonate mineral found in evaporative environments in association with other saline indicators. | ||
| 54 | Mineral | Plagioclase | Plagioclase is a term for feldspars in the Na-Ca solid solution series. Without twinning patterns, there is no way to tell a difference between Na-Ca feldspars and K-feldspars (microcline and orthoclase). | lamellar-twinning
low-birefringence |
silicate |
| 149 | Contaminant | Polycarb Large Fragment | contaminant | ||
| 150 | Contaminant | Polycarb Small Fragment | contaminant | ||
| 5 | Mineral | Pyrite | Opaque (black). Yellow in reflected light. Pleochroism and birefringence not applicable. Euhedral, framboidal, space-filling shapes. May coat or replace organic matter. Occurs in organic-rich or reduced sediments. Common in lacustrine, wetland, estuarine, and marine environments. | Opaque
euhedral |
Cubic Octahedral Framboidal sulfide |
| 138 | Mineral | Pyroxene | A class of aluminosilicate minerals, many of them iron and/or magnesium-bearing, having wide distribution in igneous and metamorphic rocks and occurring commonly as minor but often prominent constituents in sedimentary environments. In smear slides, Mg-Fe pyroxenes are typically shades of green or brown (depending on mineral species) in plane-polarized light, often display moderate to strong pleochroism, and show moderate birefringence in cross-polarized light. Extinction can be either parallel (minerals in the orthopyroxene class) or inclined (clinopyroxene minerals). Pyroxene minerals have relatively high specific gravity, and will tend to concentrate with other heavy mineral species in winnowed or density-sorted depositional environments. | silicate | |
| 47 | Mineral | Quartz | Transparent colorless; equant grains; cleavage absent. Grains larger than ~30um show higher order birefringence colors (dark orange, pink), while smaller grains appear white or gray in cross-polarized light. May appear pitted, or show opaque or reddish coatings visible in plane polarized or reflected light. May be well-rounded where aeolian or fluvial transport contributes. Common mineral in detrital sediments and rock fragments. | Low-birefringence
Equant |
silicate Transparent Colorless Low-relief |
| 60 | Mineral | Rhodochrosite | Greenish-brown in plane light. Strongly pleochroic. High birefringence. Ellipsoidal; may be difficult to distinguish in smear slide from siderite or dolomite. Forms in environments with reduced Mn. Occurs in lakes and estuaries, but uncommon; rare to absent in marine settings. | Brown-green
High-birefringence |
|
| 120 | Mineral | Rutile | Transparent gray-green. Nonpleochroic. Strong second-order birefringence with vivid colors. High relief.
Usually detrital, but in rare cases may form diagenetically (M. Talbot, pers. comm). May appear as multiple contact twins. |
high-relief transparent twinned heavy-mineral |
|
| 42 | Mineral | Serpentine minerals | A group of hydrous silicate minerals including the fibrous (asbestiform) mineral chrysotile and related members of the kaolinite-serpentine group, occurring primarily through metamorphic alteration of ultramafic rocks. | ||
| 97 | Mineral | Siderite | Transparent pale green to orange-brown. Nonpleochroic. High-order birefringence. Moderate relief.
Form is somewhat diverse, due to varying means of formation. Common forms are elongate laths with squared off ends and parallel sides (easily distinguished from rice grain shaped aragonite and more rhombic calcite), twinned "bowtie" shapes of multiple laths, or granular rounded euhedra. Requiring reduced iron, siderite, FeCO3, usually forms deep in the water column, when anoxic bottom waters mix with carbonate-rich surface waters, or diagenetically. Massive amounts of siderite may be precipitated rapidly, and may or may not be cemented with siderite or other phases. |
carbonate green brown |
|
| 151 | Contaminant | Slide Glass | Slide manufacturing and handling can sometimes produce fine shards that mimic volcanic glass. Pre-cleaning of new slides prior to smear slide preparation can help minimize encounters with this confusing artifact. | isotropic conchoidal-fracture | contaminant |
| 73 | Mineral | Sulfur | Diagenetic elemental sulfur occurs rarely as yellow nodular masses in sulfate-rich, iron-poor lake systems with active sulfate-reducing microbial communities. | ||
| 61 | Lithofacies | Tephra | Tephra, or volcanic ash, is a mixture of volcanic glass and crystalline grains derived from the same volcanic source. A tephra unit in a core may be predominantly crystalline and coarse-grained at the base, grading upwards to finer, more glassy grains. See volcanic glass for a detailed description and identification; crystalline components can be identified based on their optical mineralogical characteristics.
Isotropic conchoidally fractured volcanic glass (typically dominant) in variable proportions with crystalline volcanic constituents. Glass may be altered to any of a suite of secondary minerals, typically of low and variable birefringence. |
volcanic-glass isotropic conchoidal vesicular |
|
| 172 | Lithofacies | Tephra - Glacier Peak G | Lithofacies defined as the directly deposited ejecta from the 'Series G' Plinian eruption of Glacier Peak, Washington state, ca. 13500 cal. yr BP.
Distinguished indisputably by elemental chemistry. Identification is frequently inferred by bracketing ages, geographic distribution, and general appearance. |
volcanic-glass isotropic conchoidal vesicular Cascades |
|
| 179 | Lithofacies | Tephra - mafic | Lithofacies defined as the directly deposited ejecta of mafic (typically basaltic) volcanic eruptions. | ||
| 177 | Lithofacies | Tephra - Mount Saint Helens Y | Lithofacies defined as the directly deposited ejecta from the 'Series Y' eruption of Mt. Saint Helens, Washinton state, ca. 3750 cal. yr BP.
Distinguished indisputably by elemental chemistry. Identification is frequently inferred by bracketing ages, geographic distribution, and general appearance. |
volcanic-glass isotropic conchoidal vesicular Cascades |
|
| 173 | Lithofacies | Tephra - Mt. St. Helens J | Lithofacies defined as the directly deposited ejecta from the 'Series J' eruption of Mt. Saint Helens, Washinton state, ca. 12000(?) cal. yr BP.
Distinguished indisputably by elemental chemistry. Identification is frequently inferred by bracketing ages, geographic distribution, and general appearance. |
volcanic-glass isotropic conchoidal vesicular Cascades |
|
| 176 | Lithofacies | Tephra- Mazama | Lithofacies defined as the directly deposited ejecta from the cataclysmic Plinian eruption of Mt. Mazama, Oregon, ca. 7630 cal. yr BP.
Distinguished indisputably by elemental chemistry. Identification is frequently inferred by bracketing ages, geographic distribution, and general appearance. |
volcanic-glass isotropic conchoidal vesicular Cascades Holocene |
|
| 185 | Mineral | Titanite | Very high-relief Ti-Ca silicate mineral with prominent acutely angled twinning.
High birefringence, but high optical relief may obscure interference colors in small detrital grains. May occur as part of winnowed heavy-mineral assemblages in littoral sediments or as part of heavy-mineral lag deposits on surfaces of aeolian deflation. |
high-birefringence | |
| 118 | Contaminant | Toothpick | Small fibers from wooden toothpicks used to disperse sediment on smear slides can be confused with muscovite. Transparent, colorless. Strong second-order birefringence. Shredded or stringy texture common. Low relief. Cellular structure may be visible and can be used to distinguish toothpick from muscovite | Shredded
Stringy Colorless High-birefringence Cellular-structure |
contaminant |
| 71 | Mineral | Tourmaline | Transparent, variety of colors or colorless. Pleochroic (variable with composition). Moderate birefringence giving vivid colors. Elongate prismatic crystals to rounded grains. Moderate to high relief. Straight extinction. Often has inclusions. | Prismatic
Pleochroic Heavy-mineral |
silicate moderate-birefringence elongate high-relief |
| 112 | Mineral | Trona | Colorless (sometimes cloudy), prismatic or acicular, moderately high relief and high birefringence; may be striated parallel to long dimension. Trona is an evaporite mineral formed in hypersaline lakes or as an efflorescent precipitate on sediment surfaces. Highly soluble in water, and will dissolve and re-precipitate during smear slide manufacturing if water is used; slides should be made using ethanol if the presence of evaporate minerals is suspected. | high-birefringence
striated monoclinic-habit water-soluble |
|
| 165 | Lithofacies | Turbidite sequence | Lithofacies comprising one or more graded beds, interpreted as the product of gravity-driven mass transport and density separation of sediment constituents.
Sharp, sometimes erosional basal contact; normal (fining-upward) size grading; may have distinctive light-colored uppermost layer of fine silt or clay-sized material; may have relative concentration of heavy minerals at deposit base. |
graded density gravity-deposit Bouma-sequence |
|
| 59 | Mineral | Vivianite | Blue in both plane and cross-polarized light. May occur in diagenetic sprays, euhedra, nodules, and coatings. Low birefringence. In core face, chalky white when reduced; bright blue when oxidized. Associated with organic matter, bones, teeth, seeds, and other environments with available phosphate and reduced iron. Commonly found in lacustrine and estuarine sediments. Not common in marine sediments. | Blue
Pleochroic |
phosphate transparent diagenetic ferrous |
| 27 | Mineral | Volcanic Glass | Transparent colorless to pale gray, green, or brown. Nonpleochroic. Isotropy is diagnostic feature, although devitrification may cause low-order birefringence at edges of grains. Moderate relief. May have bubble or pipe vesicles, stretching textures, cuspate to lunate bubble wall shards with sharp edges. May be disseminated throughout other sediment or occur in pure layers. Tephra may also contain crystalline grains from the same eruption or reworked material. | Isotropic
Vesicular |
bubbles shards sharp ash |
| 49 | Mineral | Zeolite | Class of hydrous aluminosilicate minerals commonly occurring through alteration of volcanic glass. Common zeolite minerals (phillipsite; clinoptilolite) are weakly birefringent, colorless or faintly yellowish, tabular or prismatic. Phillipsite may form cruciform twins or rosettes. Associated with volcaniclastic sediments and their alteration products. | ||
| 70 | Mineral | Zircon | Transparent colorless to pale pink. Nonpleochroic. High order birefringence and characteristically vivid interference colors in cross-polarized light. Elongate or stubby euhedra, often with inclusions aligned along the long axis of the grain. Very high relief. Straight extinction. | Heavy-mineral
High-relief |
silicate inclusions nonpleochroic high-birefringence transparent |
| 152 | Contaminant | Zorbitrol | Zorbitrol is a hydrophilic sodium acrylate polymer sometimes used to physically stabilize the surface of sediment cores. | contaminant |
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