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Id 61
Identification Type Lithofacies
Name Tephra
Distinguishing Features isotropic
Description 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.
Tags volcanic-glass
External Resources
Imposters
Images
Unique Identification: Tephra
Site name: Jones
Light type: Plane-Polarized Light
Magnification: 400.0
Submitted by: Mark Shapley
Notes: glassy vesicular stretched
Image Tags: none
Unique Identification: Tephra
Site name: Jones
Light type: Cross-Polarized Light
Magnification: 400.0
Submitted by: Mark Shapley
Notes: analyzer <90 deg. glassy vesicular stretched
Image Tags: none
Unique Identification: Tephra
Site name: Jones
Light type: Plane-Polarized Light
Magnification: 100.0
Submitted by: Mark Shapley
Notes: prominent mafic minerals typical of GP. mineral-rich
Image Tags: none
Unique Identification: Tephra
Site name: Jones
Light type: Cross-Polarized Light
Magnification: 100.0
Submitted by: Mark Shapley
Notes: prominent mafic minerals typical of GP. mineral-rich
Image Tags: none
Unique Identification: Tephra
Site name: Redfish Lake, ID
Light type: Cross-Polarized Light
Magnification: 100.0
Submitted by: Shapley
Notes: Glacier Peak(?) crystal-rich tephra
Image Tags: tephra volcanic-glass crystalline mafic minerals
Unique Identification: Tephra
Site name: Redfish Lake, ID
Light type: Plane-Polarized Light
Magnification: 100.0
Submitted by: Shapley
Notes: Glacier Peak(?) crystal-rich tephra
Image Tags: tephra volcanic-glass crystalline mafic minerals
Unique Identification: Tephra
Site name: Redfish Lake, ID
Light type: Cross-Polarized Light
Magnification: 400.0
Submitted by: Shapley
Notes: Glacier Peak(?) crystal-rich tephra
Image Tags: tephra volcanic-glass crystalline mafic minerals
Unique Identification: Tephra
Site name: Redfish Lake, ID
Light type: Plane-Polarized Light
Magnification: 400.0
Submitted by: Shapley
Notes: Glacier Peak(?) crystal-rich tephra
Image Tags: tephra volcanic-glass crystalline mafic minerals
Unique Identification: Tephra
Site name: Redfish Lake, ID
Light type: Cross-Polarized Light
Magnification: 400.0
Submitted by: Shapley
Notes: Quenched glassy rind coating euhedral feldspar grain
Image Tags: feldspar volcanic-glass overgrowth tephra
Unique Identification: Tephra
Site name: Redfish Lake, ID
Light type: Plane-Polarized Light
Magnification: 400.0
Submitted by: Shapley
Notes: Quenched glassy rind coating euhedral feldspar grain
Image Tags: feldspar volcanic-glass overgrowth tephra
Unique Identification: Tephra
Site name: not specified
Light type: Plane-Polarized Light
Magnification: 100
Submitted by: Mark Shapley
Notes: Quenched magmatic rind (glassy) prominent in side view along grain margins. From an unidentified tephra occurrence on the Kenai Peninsula, Alaska.
Image Tags: amphibole hornblende pleiochroic green prismatic quenched-rind mafic-mineral volcanic-glass
Unique Identification: Tephra
Site name: Fish
Light type: Cross-Polarized Light
Magnification: 100
Submitted by: Mark Shapley
Notes: In cross-polarized light, glassy quenched rind is invisible along grain margins, but visible as scaly texturing disrupting birefringence on the body of the amphibole grain. From an unidentified tephra occurrence on the Kenai Peninsula, Alaska.
Image Tags: amphibole hornblende pleiochroic green prismatic quenched-rind mafic-mineral volcanic-glass
Unique Identification: Tephra
Site name: Redfish Lake, ID
Light type: Plane-Polarized Light
Magnification: 400.0
Submitted by: Mark Shapley
Notes: basaltic tephra presumed to be from Craters of the Moon basaltic province
Image Tags: basaltic mafic micro-tubule Pele's-Hair
Unique Identification: Tephra
Site name: Redfish Lake, ID
Light type: Cross-Polarized Light
Magnification: 400.0
Submitted by: Mark Shapley
Notes: basaltic tephra presumed to be from Craters of the Moon basaltic province
Image Tags: basaltic mafic micro-tubule Pele's-Hair
Unique Identification: Tephra
Site name: Yellowstone
Light type: Plane-Polarized Light
Magnification: 400
Submitted by: Val Stanley
Notes: none
Image Tags: green vesicular
Unique Identification: Tephra
Site name: Yellowstone
Light type: Cross-Polarized Light
Magnification: 400
Submitted by: Val Stanley
Notes: Highly vesicular volcanic shard
Image Tags: vesicular
Unique Identification: Tephra
Site name: not specified
Light type: Plane-Polarized Light
Magnification: not specified
Submitted by: Guy Rothwell
Notes: Field of volcanic glass shards showing a wide range of shard morphology, including semi-regular fragments packed with subparallel pipe vesicles and vesicular glass fragments and bubble wall shards, foraminifera and large biotite mica flake also in the field., volcanic-glass pyroclastic pipe-vesicles shards
Image Tags: none