I've discovered that there can be a lot of confusion about the differences between geodes and vugs. According to Mindat.org, a vug is a cavity in a rock, usually lined with crystals of a different material composition than the enclosing rock.
VUGS YOU LOVE
This is my very favorite vug. It's only about two inches at it's longest point and the cavity is a bit over one inch deep,but it's full of character. When I hold it in hand, it mostly looks brown, but you get it near lights and it turns into a star. I think the green is olivine and the orange spears are wolfenite.
HOW DO YOU IDENTIFY A VUG?
According to Mindat.org, a vug is a cavity in a rock, usually lined with crystals of a different mineral composition than the enclosing rock.This fanciful vug is lined with crystals that appear to be quartz. But as someone who is always trying to listen to the rocks,all I see is an angry swirl with some crystal linings. Not a happy vug at all.
YET DISTINCT FROM A GEODE
An open space in a rock is not necessarily a geode. To be a geode, the open space in the matrix must have a shell-like outer layer with crystal growth geodes:
The shot below shows another face of the same rock with empty vugs shown. When I cut this, I REALLY hoped I'd find some more garnets, but sometimes a hole is only a hole.
The thing that makes this picture interesting to me is that the vugs are shown here at several levels of development from the dark spaces that are somewhat friable to finished crystal-lined shapes.
In this case the geode slice shows inclusions at the 4 o'clock and 6 o'clock positions.
ROCK & GEM MAGAZINE FEATURE!
If you are a subscriber to Rock & Gem Magazine, don't miss my article in the January issue about Intarsia/Pietra Dura. It profiles the craft and the history of this artistic craft through the vision and accomplishments of renowned artist Naomi Morgan.
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I wish all my readers the joy and blessings of the holiday season, however you celebrate it.
Your Lapidary Whisperer.