Scottish Gemmological association
Wednesday, October 30th, 6.30 for 7.00pm
(please note early start)
Marco Campos Venuti, speaking on Agates - ¨The Big Band Theory¨
An insight in shape modelling of banded agates.
About the talk: First we have to understand that natural silica is not a mineral, but a polymer. This is a completely new world with a different physics than classical mineralogy. The main differences are the slow passage from liquid to solid (in crystals, atoms are in full solution and one second after, they are solidly bound to a crystal lattice) and that solidification is reversible. The processes are water driven at room temperature, so we are in a pedogenetic environment, a few meters inside the soils.
We usually think crystals are grown in millions of years, but they are subjected to very slow chemical and physical variations. To the contrary, in soils every rain and every change in season strongly influences the formation of the agate. And they are formed in a few years!!
With our study we opened a window in the agates formation that enlightens much information on the past geological history.
Marco Campos-Venuti has been a stone collector since his childhood. He has studied and taught geology, he is a tireless lapidary, a respected gem dealer, a gem expert for an online auction house and he writes a lot about stones. Firstly about Volcanology when at University and later about minerals and gemstones. He was editor of the Rivista Gemmologica Italiana for 7 years and he has written two monographic books about agates and jaspers formation.
Marco created a genetic model for the formation of agates and jaspers using his huge collection as a database for the geological analysis. Some important topics of his investigation focused on the mechanism of formation of many of the structures present in silica minerals:
the formation of thunder eggs
the genesis of orbs in some jaspers
the formation of orbicular jaspers by devetrification of obsidians
the unexpected auto brecciation process in jaspers
the dilution and dissolution in banded agates
the genesis of fire agates
the formation of moss and plumes in agates
the many disequilibrium processes between the three silica polymers: chalcedony, jasper and opal
and the important interaction between bacteria and silica minerals.
Wednesday, November 27th, 7.00 for 7.30pm.
Elizabeth Passmore, speaking on Jewels by Andrew Grima, illustrated by the style, gemstones and stories of some of his creations.
Andrew Grima was one of a handful of British designers who revolutionised jewellery in the early 1960s. Unlike most of his contemporaries, he didn't learn his trade at art school, being entirely self-taught and having never worked at the bench. He considered being a pure designer to be an advantage; his ideas were never confined by technical ability, only by imagination.
Elizabeth has had a life-long interest in gemstones and jewellery. She is a member of the Scottish Gemmological Society, the Gemmological Association of Great Britain and the the Society of Jewellery Historians. Following her retirement after a life in education she has been studying the jewellery of Andrew Grima, one of the most influential jewellers of the second half of the 20th century. She will be giving an illustrated talk about his jewellery and will have some examples of his pieces to show us.
Elizabeth is very grateful for the assistance and input she has had from the Grima family in preparing this talk.
We are continuing to hold our Monthly Meetings at the Eric Liddell Centre, located on the southside of Edinburgh at:
It is just past the junction of Bruntsfield Place, Colinton Road and Morningside Road. Evening parking in this area usually presents no problems and the Centre is served by Lothian buses services 5, 11, 16, 23, 45.
If you would like to join us afterwards just for a coffee, a drink or something to eat, we will have a table booked at the nearby Cafe Grande.
Our Whitby and Castleton Trip