The book
Genesis and Classification of Agates
and Jaspers: a New Theory
Marco Campos-Venuti

in English
Deciphered one of the biggest mysteries of geology!
A guide to the collector.
A Bible for the geologist.


NOW AT ONLY: 35 Euros + 10 Euros for Worldwide shipping = 45 Euros

160 pages, 437 pictures,  22 diagrams deeply investigate about the formation of microcrystalline and amorphous silica.
This book shows a new geological model that explains the formation of most of the microcrystalline and amorphous varieties of silica. It has been written for the collectors, the geologists and for the curious, analyzing many collectible varieties of jaspers, agates and chalcedonies. The use of a geological and stratigraphic innovative approach to the theme, leads to the consequence that most of the concepts are original. Jasper and Chalcedony result to be two silica polymers.

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.

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.


Genesis of the first chalcedony layer
Origin of mosses and plumes
Formation of bands
Primary and secondary colors
Connective channels and interruptions of the bands
Horizontal and concentric banding
Quantitative analysis
Morphology of the bands
Stratigraphy of a banded agate
Influence of climatic conditions
Types of agate depending on host rock
Origin of colored chalcedony without bands
Banded agates without the first chalcedony layer
Lace and Beacon Agates

Classification of Jaspers
Flints and abyssal jaspers
Genesis of orbicular jaspers
Precursors of jaspers
Thunder egg formation
Orbed jaspers
Brecciated jaspers
Chemical disequilibrium between jasper and chalcedony
Classification of non-crystalline silica
Table of contents of the book

The theory has been presented at:
CIGES 2012 (Convegno Italiano Gemmologia Scientifica) in Florence, Italy
25-September-2012    "Una nuova teoria sulla genesi dei diaspri e dei calcedoni"
(in italian with english slides)

IGE (Instituto Gemológico españolo) in Madrid, Spain
16-October-2012    "Jaspes y ágatas, polímeros de la sílice" (in spanish)
The talk (in spanish) can be viewed at:

G.A.M. Sevilla, Spain
22-Juin-2013    "Jaspe, polímero de la sílice: Origen y Clasificación" (in spanish)
28-December-2013    “Agatas: concreciones de Calcedonia” (in spanish)

Tucson Mineral Lecture Series 2015 at Pueblo Gem and Mineral Show, Tucson, Arizona
9-February-2015    "Agates, Jaspers, Opals: Polymers between Crystals" (in english)
(For the audio recording contact

Review by Mark Oros at:

Review by Bob Jones in Rock & Gem, February 2013

Review by Tony Nikischer in Mineral News, March 2013

The author is available for a 4 hours lecture on the subject or a short course.
Contact for rates:

You can learn here about the new classification of jaspers in 4 types:
Classification of Jaspers
Jasper 1 Jasper 2 Jasper 3 Jasper 4

hold in microvideos  by Marco Campos-Venuti (in ENGLISH) 

tenuto in microvideo da Marco Campos-Venuti (in ITALIANO)