Title
Graywacke
Alternative Title
Siltstone
Identifier
FR-13
Description
Equal mix of angular and rounded sand-sized grains of quartz, with clay sized feldspars. Surface contains significant coverage of calcite that formed after lithification. Fresh surfaces do not effervesce with acid meaning that reaction is based on secondary calcite formation.
(Thin Section FOV: 1.28mm)
(Thin Section FOV: 1.28mm)
Date
Not given
Contributor
Western Minerals, Inc.
Spatial Coverage
In an old quarry just east of state Highway 1 just south of the town of Tomales in the northern part of Marin County.
Temporal Coverage
Mesozoic
Accrual Method
Purchased from Western Minerals, Inc.
Number of Thin Sections
1