From:
"Dr. Tim Palmer" <tjp@xxxxxxxxxx>
Date:
Thu, 19 Jul 2001 19:28:07 +0100
Subject:
name that stone
Anthony,
Don't get too caught up with that thing about the
angles. You need to be sure that you're looking at the
breaks WITHIN individual crystals to be certain that
you're looking at what geologists call mineral cleavage
(which is diagnostic of the different mineral classes).
Many lumps of stone will break perpendicular (i.e. form
right angles) to existing surfaces when you strike them,
because that produces the new broken face with the
smallest area (so requiring the minimum input of
energy).
Sounds like you may be using good old
sandstone/quartzite, or an igneous rock with quartz in
it. The quartz is harder than ordinary steel (hence the
metal trace left on the surface when you try to scratch
it), but a lot softer than diamond or aluminium oxide
grinding wheels.
Tim
- References
- message 00038: name that stone - anthony_marbella Last Name (10 Jul 2001)
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