GEODES
Geodes begin as bubbles in submarine limestone or lava flows and trap dissolved minerals inside. As the minerals harden, layers of projecting quartz crystals, often purple amethyst, or wavy haloes of brilliantly hued mineral agate form inside the geode. Geodes are found in the United States and Mexico, but in greater quantity in Brazil.
http://www.artgeo.com/shop/merchant.mv?Screen=CTGY&Store_Code=AG&Category_Code=GH
http://www.amonline.net.au/factsheets/geodes.htm
Concretions, Thunder Eggs and Geodes
http://www.umd.umich.edu/casl/natsci/geology/mineral/geodes.html
http://oh.essortment.com/whataregeodes_rtll.htm
What are geodes?
http://www.ugs.state.ut.us/utahgeo/rockmineral/collecting/rkhd0500.htm
Dugway Geode Beds, Juab County
http://www.madsci.org/posts/archives/may98/892420341.Es.r.html
Why do geodes have crystals on the inside and not on the outside?
http://volcano.und.nodak.edu/vwdocs/frequent_questions/grp9/question2005.html
What are the origin of geodes (thundereggs)?
http://www.minerals.net/mineral/silicate/tecto/quartz/varietys/geodes.htm
The term geode is derived from the Greek language and means shape of the Earth. This can be an accurate statement since geodes are often easy to spot due to their spherical shape. Geodes are defined by their cavity which is lined with crystals.
http://www.wildearthproducts.com/Products/Geodes/geodes.html
http://wheretofindagate.com/geodes.htm
http://www.desertusa.com/magjan98/jan_pap/du_rock_geode.html
http://www.isgs.uiuc.edu/servs/pubs/geobits-pub/geobit3/geobit3.html
Geodes
They are useless,
there is nothing to be done with them,
no reason, only the finding:
letting myself down holding to ironwood
and the dry bristle of roots into the creekbed,
into clear water shelved below the outcroppings,
where crawdads spurt through silt;
clawing them out of clay, scrubbing away the sand,
setting them in a shaft of light to dry.
Sweat clings in the cliff's downdraft.
I take each one up like a safecracker listening for the lapse within,
the moment crystal turns on crystal.
It is all waiting there in darkness.
I want to know only that things
gather themselves with great patience,
that they do this forever.
http://jaredcarter.com/poems/1/
