I'm sorry I haven't responded to you sooner - lots of "stuff" happening. Hi and welcome - it's noce to have other SA citizens on this - Sometimes it feels like we wren't part of the greater global world doesn't it....
Bargello had not occurred to me as being geological, but I just looked at Su's work on TangleCrafts and I can see some real potential there! I can especially imagine something about lava and volcanic explosion!
Welcome to Stitchin' Fingers, Dee. I am intrigued by your question on the Design group - as I mentioned there. I worked for US Geological Survey for two years, so I can attest to there being a LOT of options for a geological theme. Don't be shy about telling the group more, but if you want to keep it quieter I would enjoy discussing some ideas with you.