 | near Port Ludlow, Washington |
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GEOLOGY
Crescent Formation - Late Paleocene to middle Eocene (62-48 Ma). The Crescent Formation is comprised of a large volume of submarine/subaerial basalt. The Crescent basalts are among the oldest basalts in this region and makeup the basement of the Coastal range. Babcock et al. (1992) concluded that the Crescent Formation basalts erupted into a subsiding rift basin along the western coast approximately 60 mya. Exposure of the Crescent Formation can be found as a continuous swath defining the northern, eastern, and southeastern edge of the Olympic Peninsula. Based on gravity studies, the Crescent Formation is thought to extend eastward beneath the Puget Sound to Seattle. Most of the Crescent Formation, especially on its eastern edge, is covered with Quaternary glacial till deposits.
Multiple basalt flows exposed at this dormant quarry contain vesicles that show a complex history of sub-greenschist facies (zeolite) mineralization. Mineralization is most prevelant directly above contacts between individual flows. This localilty is listed in a mineral collecting pamphlet issued by the Washington State Mineral Council. Access may be subject to change.
MINERALS (incomplete list) CLICK for COMPLETE LIST
| CaCO3 - Flourescent white to bright yellow crystals in a variety of habits are found within amygdules. | |||||
| Fe endmember chlorite - (Fe,Mg)3Fe3(Si,Al)4O10(OH)8 - Some amygdules are lined with fine-grained dark green to black platey masses. | |||||
| Cu - Micromount specimens of copper include wirelike forms and individual crystals. | |||||
(Ca,Na2,K2)Al2Si4O12·6H2O
- Rare mm-scale milky white hexagonal plates, some with red/orange iron-oxide inclusions.
| SiO2
- Drusy quartz is found associated with green jasper.
| NaCa2Al5Si13O36 . 16H2O
- Small colorless crystals line some amygdules.
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* photographed
CALCITE |
Drusy
QUARTZ spheres |
STILBITE,
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Drusy QUARTZ,
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LEVYNE |
COPPER wire on CLINOCHLORE |
CALCITE on CLINOCHLORE |
Babcock R. S., Burmester R. F., Engebretson, D. C., Warnock A., Clark K. P. (1992) A rifted origin for the Crescent basalts and related rocks in the northern Coast Range volcanic province, Washington and British Columbia. Journal of Geophysical Research, B, Solid Earth and Planets 97;5, 6799-6821.
