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The inclusions and structures in agates tell us substantialinformation about the conditions of agate formation omitted from our literature. When the agates have lava shells as geodes,that lava tells us where the agates formed.We can use reflectance infrared spectroscopy to reveal what thismineralization is in many cases when in high enough concentration.
From that, this book proposes and presents the data tosupport the model view that the Lake Superior agates did not form fromweathering, but instead formed directly in basalts that were latermetamorphosed in lava flow tops that were highly vesicular, around Cretaceous,whose silica was enhance by substantial outfalls of volcanic ash coming fromMidwest volcanics at that time.
This book starts with the published photos provided from aprior book by the famous collector John Marshall who was very curious aboutthese agate inclusions, and adds to that with specimens the author purchased andspecimens loaned from collectors.Microscopy and infrared spectroscopy were used to study specimens, andmineralization is link to specific geochemistry found in the literature.
The book is 8.5 x 11 inches, plastic comb bound, 208pgs. First published in 2011, last updatewas in 2021.
