Jasper and Chalcedony are two silica polymers. They are formed as concretions in surface rocks.
This leads that silica varieties take their origin in a meteoric environment with a strong influence due to the weather and the alternation of dry and wet seasons. Uncountable situations are possible due to the many parameters as the host rock, the pH of the water and the latitudes, that explain the numerous existing varieties of silica.
Explication of the involved phenomena is ruled out with the help of an endless number of pictures and diagrams that capture and maintain the attention of the reader.
About the author:
The author born in 1965. Is a PhD volcanologist and editor of the “Rivista Gemmologica Italiana”. Since his childhood he is a passionate collector of stones, and was always curious to investigate their origin. He has an important collection of agates and jaspers and has written innumerable scientific papers.