Gary Navarre on mon 6 sep 04
Pat and Crew,
Igneous rocks have three classifications. Intrusive, formed at great
depths, cooling vary slowly and forming large crystals. Hypabyssal, formed
at medium depth, cooling moderately slow forming medium size crystals.
Volcanic, solidified at the surface, cooling quickly forming fine grained or
glassy textured rocks. Volcanic rocks can be of any age from Precambrian to
recent. (Paraphrased from Cardew )
Since the Canaries are in the Atlantic East of the mid-ocean spreading
they are relatively young.
We in Michigan also have a black sand that is wave sorted in thick strips
along the shore of Lake Michigan. I used a gold pan to collect some to
sample in my wood kiln. After grinding for a while by hand (m&p) I dipped a
glaze brush in the fines and added accents to the surface. It turned out
quite interesting with tiny red, green, and black streaks from the particles
in the glaze. I'd say this is basically a magnetite sand (it was magnetic)
transported from the Iron and Copper ranges of the U.P. via. glaciers and
water.
Just grind some up, put it on a pot and see what happens.
Gary Navarre
Navarre Pottery
Norway, Michigan, U.S.A.
----- Original Message -----
From: "Pat Southwood"
To:
Sent: Sunday, September 05, 2004 2:59 PM
Subject: black beach sand.
Hi List,
Just got back from the Canaries and confess to bringing home a little bit
of black volcanic sand.
Is it fresh (ish) igneous rock?
Yours,
Pat Southwood.
pat@southwwod4.fsnet.co.uk.
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