SFBWR Serpentinite's Glow Earthcache EarthCache
SFBWR Serpentinite's Glow Earthcache
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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.
This is one of a set of earthcaches that are part of the hiking trail system at Don Edwards San Francisco Bay National Wildlife Refuge. You may park at the visitor center to begin your journey. BE SURE that you have downloaded a copy of the trail map (visit link)
before beginning your hiking journey.
Logging Requirements:
Send the answers to #1-#4 to me through my geocaching profile.
1.List the name “GC2EV70 SFBWR Serpentinite 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.Measure the SIZE (width and height) of the large boulder at the cords
4. Compare the EFFECT of weathering on the luster of this rock (its is a rather new face) compared to the larger boulder found at N 37 31.669 W 122 04.110. HOW DOES WEATHERING (the rain, sun, etc.) affect the luster you identified above?
5. Post a picture of yourself and/or your GPS with your log that shows the large boulder from requirement three. If you are opposed to a picture, please state WHICH SIDE of the trail the boulder is on (north, east, west, south).
I will only respond if you have incomplete logging requirements. Go ahead and log your cache
At this site you can view a good sized boulder of serpentinite. It is rather weathered on the surface, so before answering the logging question about luster, be sure to FIND a “fresh face,” that is a place where the face of the rock has been newly exposed.
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. 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. PLEASE DO NOT ATTEMPT TO COLLECT ANY ROCKS FROM THE NWR!
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
waxy -- like the surface of a candle
greasy / oily
pearly -- like a pearl, play of colors, light
silky -- has a shiny surface like a piece of silk cloth
glassy / vitreous -- looks like glass quartz, many rock-forming minerals "nature’s glass"
resinous -- looks like freshly-broken shellac, usually yellow-brown
adamantine -- high luster, almost brilliant, "diamond-like"
sub-metallic -- silvery or metallic luster but mineral is transparent or translucent when in small slivers
metallic -- very shiny, like processed metals, highly reflective, opaque minerals
History/Extraneous Information
Resources:
Alt & Hyndman, Roadside Geology of Northern andCentral California. Mountain Press Publishing. Missoula: Montana. 2000.
Don Edwards SF Bay Wildlife Refuge – (visit link)
Additional Hints
(No hints available.)
Treasures
You'll collect a digital Treasure from one of these collections when you find and log this geocache:
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