Inorganics

Id Identification Type Name Description Distinguishing Features Tags
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

Contact Information

CSD Facility

116 Church Street NE, Minneapolis, MN 55455

P: 612-626-7889

Connect on Social Media