January
9, 2010 Dave Hart and I met at one of the
spots in Wake County where
alpine-type fissures are exposed near the surface. Smokey
quartz crystals and rutile can be found here.
Here's a brief video of Dave finding crystals. At the end of the video I'm holding a very large three sided half formed crystal.
This
is a perfect example of what I refer to as an "EOD". Or edge of dike
piece. These form by a pre-existing hardened and solidified dike within
a softer and more malleable and highly heated matrix of schist deep in the earth.
As the forces related to mountain building push, pull, and stretch the
matrix , the harder less malleable dikes leave pockets next to them as the softer
schist deforms around it. These pockets are later filled with
highly heated fluids carrying desolved silica and other minerals such
as rutile and siderite. The area on the dike around where the pockets
form (usually on one edge or side of the dike) become crystallized.
I believe this piece may have started as a regular uncrystallized dike and then later became crystallized on the one side of it (top side in the picture) where the pocket formed.
