Serpentinite’s Luster of Lake County Earthcache EarthCache
Serpentinite’s Luster of Lake County Earthcache
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Difficulty:
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Terrain:
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Size: 
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As an earthcache, there is no “box” or “container” to discover. Rather, with this cache, you discover something about the geology of the area. For more info, consult www.earthcache.org
There is a wide spot JUST SOUTH of the large roadcut. The earthcache location is about 50’ away from the road so you won’t need to worry about being annihilated by zooming cars! It is at a spot that allows easy pull out back into traffic...I hope.
Logging Requirements:
Send the answers to #1-#4 to me through my geocaching profile. DO NOT post the answers to any logging requirements on this site.
1. List the name “GC2544W Serpentinite Luster of Lake County Earthcache” in the first line of your email. Also, list the number of people in your group.
2. What type of LUSTER do you see in this selection of serpentinite?
3. Other than light green, what are two of the other colors of rock in the serpentinite – THAT SHARE THE SAME LUSTER – and that you see in the rock field in front of you?
4. Measure the SIZE (width and height) of the largest outcropping near the cords (about 20’ east-northeast of the cords).
5. (Per current gc.com guidelines, photos are no longer allowed to be required. HOWEVER they are encouraged, since they can help clarify that you have visited the location if your other logging requirement answers are vague). Post a picture of yourself and.or your GPS with your log that shows the large boulder from requirement 4. If you are opposed to a photo, you may tell me what geological erosion feature is actively taking place about 100’ southwest of the cords (lower elevation, on the same side of the road)
I will only respond if you have incomplete logging requirements. Go ahead and log your cache
Geology:
California’s state rock, Serpentinite, is a volcanic rock formed deep within the earth’s mantle. It is highly viscous as it slithers up through the cracks and crevices, metamorphizing as it squeezes and cools as it nears the earth’s surface (usually from underwater, at least initially). The cooling(ed) rocks slide past each other in blocks, becoming HIGHLY polished in the process. Finally, they squeeze through the earth’s surfaces along the California coastal range and coast usually as dark green or yellowish green exposures – and especially evident in roadcuts where they have NOT weathered out to less lustrous forms. There are several places along Hwy 29 where this rock squeezes through the surface. This is the closest large and easily accessible exposure to the towns of Middletown, Lower Lake, Angwin, and St. Helena.
Interestingly, serpentinite creates a very poor soil. In color it degrades to a reddish soil with few plants able to survive in its nutrient deficient dirt.
Luster:
This is the term used to classify what a mineral looks like in the light. You will need to examine the list below and successfully classify the serpentinite at your feet to fulfill one of the logging requirements
• dull / earthy -- very dull, mainly in minerals that are porous -- kaolinite, orthoclase
• waxy -- like the surface of a candle -- opal, chalcedony
• greasy / oily -- nepheline
• pearly -- like a pearl, play of colors, light -- talc, muscovite mica
• silky -- has a shiny surface like a piece of silk cloth -- some varieties of gypsum, kernite, ulexite & in fibrous minerals
• glassy / vitreous -- looks like glass quartz, many rock-forming minerals -- obsidian – "nature’s glass"
• resinous -- looks like freshly-broken shellac, usually yellow-brown -- sphalerite
• adamantine -- high luster, almost brilliant, "diamond-like" -- sphalerite
• sub-metallic -- silvery or metallic luster but mineral is transparent or translucent when in small slivers -- hematite
• metallic -- very shiny, like processed metals, highly reflective, opaque minerals -- pyrite, gold, silver
Resources:
Alt & Hyndman, Roadside Geology of Northern andCentral California. Mountain Press Publishing. Missoula: Montana. 2000.
Rocksforkids.com -- (visit link)
Additional Hints
(No hints available.)