 | near North Bend, King County, Washington, USA |
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LOCALITY IMAGES
GEOLOGY
Snoqualmie Batholith - late Oligocene to early Miocene (28 Ma[million years ago] to 22 Ma). Uplift and erosion of the Old Cascade Volcanic Arc exposed plutonic rock of the Snoqualmie Batholith near Snoqualmie Pass. Intrusive rock types found within the Snoqualmie Batholith range in composition from granite to gabbro. Granodiorite is the most prevalent exposed rock type. Other lithologies within the batholith include porphyritic dacite, andesite, aplite, and intrusive breccia (Livingston, 1971).
Intrusive breccias can be the host for metallic ore deposits and aesthetic mineral specimens. An intrusive breccia is a cylindrical structure that is formed by the violent ascent of volatiles near the top of a shallow intrusion as it cools. The force of volatiles escaping to the surface causes the rock to fracture and fault, providing open spaces for subsequent mineralization by hydrothermal fluids. These high temperature acidic fluids are responsible for the alteration of plagioclase to muscovite and clay within the adjacent granodiorite breccia blocks and for the precipitation of quartz and metallic ore (usually as sulfides) on the walls of the blocks. Most intrusive breccia metallic mineral deposits within the Snoqualmie region are currently uneconomic due to poor accesibility and/or the low tenor of the ore (Cu, Au, Ag), but many mining claims are still active that produce some of the finest quartz and sulfide mineral specimens in the world.
The Clipper View Claim is in the vicinity of the Clipper Zone of the NE trending Middle Fork property. All specimens below were collected from a private claim. Collecting is prohibited without permission.
MINERALS (incomplete list)
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| FeO(OH)
- Occurs as late-stage (supergene) encrustations on quartz. Aesthetic spherical roses after siderite can be found. |
| FeS2
- Crystals to about 0.5 cm are included within quartz crystals. Larger inclusions show perfect cubic habit. | |
| SiO2
- Crystals to 2" line vugs within brecciated diorite. Some quartz is gem quality. Scepters and Japan-law twins are found, but are uncommon. Most crystals exhibit phantoming under short-wave UV light. Many quartz crystals are inclusions-rich. A list of inclusion phases is in the process of being compiled. | |
| FeCO3
- Aesthetic spherical roses of siderite pseudomorphed to goethite can be found. Siderite is found as flattened rhombohedrons included in quartz. |
 
QUARTZ cluster with cubic PYRITE included within sceptered QUARTZ |
 
Japan-law twin QUARTZ (fluorescent phantom) |
GOETHITE after SIDERITE on QUARTZ |
Sceptered QUARTZ |
QUARTZ scepter on matrix |
Livingston, Vaughn E., (1971) Geology and Mineral Resources of King County, Washington, USA. Bulletin - Division of Mines and Geology (State of Washington) 63, Pages 200.