From: SFPhysics@aol.com
Date: Mon Jul 17 2000 - 03:36:03 PDT
From: SFPhysics@aol.com Message-ID: <a3.8b30a05.26a43b93@aol.com> Date: Mon, 17 Jul 2000 06:36:03 EDT Subject: Re: Magnetite and Micrometeorites...... black sand..........
<< So, here's my question. Where did all the iron at the SF beach come from?
> People were asking me as I was gathering the filings, and when I showed
them
> to friends later, they asked me the same question. There must literally be
> tons of iron on that beach. I haven't notice the black iron color on other
> beaches. Thanks
> Paula Weisman
>>
Hi Paula:
Besides the common magnetite a large component of the black sand is iron
nickel micrometeorites. These are found all over the globe and represent the
tons of space dust that rain down on us each day. Gold miners using the
panning method up in the high Sierra take a magnet to extract the "black
sand" from their pans as one of the last steps in panning.
The more mundane magnetite is iron oxide existing in native rock throughout
the region. From the chert in the underlying Franciscan Formation to the
Basaltic pillow lavas seen on the Waldo Grade going down to the Golden Gate
Bridge, iron is a common element of these California crustal rocks. Erosion,
wave action, etc., that break up the rock do leave the magnetite in the sand
in large quantities.
Thomas Edison patented a magnetic ore extractor that separated iron from low
grade ore and is still used today for nickel extraction. Not much is new.
Al Sefl
Itinerant Science Teacher.........
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