Lapidary and Silversmithing – Third Monday, 7:00 PM

• The program for July 15th is silicone mold making. This technique does not involve heat or pressure like the old rubber vulcanized molds. Tony will demonstrate setting up and pouring a mold and participants will be able to make a mold of their own item.Please bring an item to create a mold — any sturdy material is fine. The original item can be plastic, wood, or metal. Hollow items are not good candidates for wax casting of a molded item because they will no longer be hollow when cast and will be very heavy and use a lot of silver.

Email Lapidary@hgms.org if you have questions.

President LT Wilcox directed a group of shop assistants and helpers including Sharon Halton, Michele Marsel, Dean Wix, Logan Wilcox, Richard Good, Steve Blyskal, David Pawek, and Dave Janos in a shop work session on Thursday. The plan is to spread the knowledge around so that more than one person knows how to fix our equipment. The

objective of the session was to clean the trim saws and replace the 10-inch blades with new 8-inch blades. These are TRIM saws, after all.  After cleaning all the trim saws, they were reassembled, new blades were installed and the proper amount of coolant (rust inhibitor in water) was added.  The trim saws were then tested to make sure they worked properly. Some people carried saw bases outside to wash them out and others cleaned top plates.

All the trim saws were numbered, starting from the door, so that when people report that a saw is malfunctioning, all the shop managers will know which machine they are talking about. Currently there are 3 trim saws on the first table, with space for a 4^th. The larger saws were numbered too: HP 24 inch saw is #1, The HP 20 inch is #2 and the HP 18 inch is #3. Then there is the big 24 inch saw, Texaco. The grinding units have also been assigned numbers, starting with the Genie near the sink and going down the row to the super grinder. That will make reporting for maintenance easier!

I have been reading a fascinating and well-researched book, Biominerals: Microbial Life in Agates and other Minerals, by Marco Campos-Venuti, an Italian vulcanologist and author of numerous scientific publications and the founder and editor of the Rivista Gemmologica Italiana. He is the author of two other books about agates and jaspers, Banded Agates: a Genetic Approach and Genesis and Classification of Agates and Jaspers: a New Theory. Campos-Venuti proposes that there is an entire new eco-system that has been overlooked. Perhaps this would sound completely far-fetched if it were not for the discovery of black smokers, deep-sea hydrothermal vents found in volcanically active locations near mid-ocean ridges and hot spots. It is not surprising that such vents deposited minerals such as iron and other metal sulfides where they entered the ocean; what is surprising is that the heat, methane, and sulfides of those deposits are converted into energy in the absence of photosynthesis by extremophile bacteria and archaea which in turn support communities of tube worms, shrimp, crabs, clams, eels, and other organisms.

The Three-domain system classifies life into three domains, Bacteria, Archaea and Eukarya. Archaea are single-celled organisms which lack cell nuclei and are called prokaryotic, as are Bacteria. Eukaryotes have membrane-bound cell nuclei and are called eukaryotic (like all animals and humans). The Three-domain system diagram indicates where various organisms fall in the tree of life. There may be another group as well, called nanobacteria for want of a better name; organisms smaller but larger than viruses than bacteria which some scientists classify as non-living even though they replicate and can crystallize organic molecules. Nanobacteria may also be involved in mineralization

Extremeophiles are organisms which tolerate extremes of temperature, pressure, radiation, salinity, and pH level. Many Archaea are extremophiles, although some Bacteria and some Eukaryotes are as well. Extremeophiles have been found in hydrothermal vents, hot springs, salt lakes, deep ocean trenches and deep rock formations. Life finds a way and colonizes unexpected environments. Why all the biology? I’m getting to that.

In Banded Agates: A Genetic Approach, and Genesis and Classification of Agates and Jaspers: A New Theory, Campos-Venuti outlined a model for the abiotic processes of agate formation and explains how most agates are formed at low temperatures from colloidal solutions deposited in seasonal wet-dry cycles. The geometry of the features we call mosses and plumes, however, cannot be easily explained as abiotic crystallization, so he left the non-crystalline mosses and plumes for the current book. He maintains that the biomineralization of microbial colonies can explain many of the mineral oddities that are so fascinating to the collectors of minerals and rocks, such as pyrite suns, landscape jaspers, manganese dendrites, fairy stones and moss agates.

He claims there is an entire previously unknown ecosystem: life inside dark cavities filled with chalcedony gel, with restricted space and nutrient supply, living without light. He presents evidence that these features are in fact formed by microbial colonies and that non-crystalline inclusions in agates are therefore fossils.

Cue the outrage and furious defense of previously held theories! There should be much new research devoted to proving or refuting this statement. The first half of the book reviews bacteria, microbialites (sedimentary microbial colonies) and stromatolites (carbonaceous microbial mounds). Stromatolites were recognized many years ago as biological but thought to be extinct until discovered growing in an Australian bay.

The second half of the book covers bacterial structures of the deep biosphere, below the surface soil down to 5 kilometers on continental rock and below the oceans. Thomas Gold theorized in 1993 that up to 95% of the Archaea and Bacteria on Earth might exist in the deep biosphere. Organisms have been found in rock, in vents, hots springs and deep wells.

Campos-Venuti recognized 6 groups of living microbial colonies living in the deep biosphere:

1. Nodular microbialites forming concretions in deformable sediments
2. Interstitial microbialites growing in the porosity of rocks such as sandstone and jasper
3. Fissural microbialites growing inside crystals and in the fractures of non-porous rock
4. Microbialites in agates – colonies develop in the chalcedony gel before it hardens
5. Pseudokarstic microbialites – non-chalcedony, non-calcareous cavities where microbial colonies develop between flushes of mineral precipitates to produce banded rocks such as malachite and rhodochrosite.
6. Open space microbialites associated with thermal springs and vents

An important characteristic of these microbialites is the development of a biofilm composed of an extracellular polymeric substance produced by and enveloping the microbes. This polymer can create a tiny ecosystem in which different organisms are protected, live and feed. These biofilms are important to the development of different types of colonies and enable other substances to be trapped and help to build structures such as stromatolites and algal mounds.

To expand on #4, Microbialites in agate: in his earlier books, Campos-Venuti notes that early researchers, proposed that agates were created one band at a time by the deposition of silica-rich fluids. Then Leisegang (in 1915) developed a theory which posited that if a cavity was completely filled it would form all the bands at once and at temperatures around 200 C. This does not account for any features other than bands.

Much of this early research also led geologists to believe that agates were formed at high temperatures in volcanic environments. In the opinion of Campos-Venuti, many agates are formed at low temperatures, although a few are clearly associated with hydrothermal solutions and form at higher temperatures. Agates also form in many different potential cavities, such as petrified logs, voids in sediments, dinosaur bones and other fossils. Many do form in volcanic terrain but may do so because of the availability of silica from volcanic ash and rhyolite and the presence of cavities in basalt and of many faults and cracks in those formations. The inclusions we call plumes and mosses are more common in igneous rock than in sedimentary formations.

Ground water containing minerals, organic material and microbes which are capable of multicellular organization enters hidden cavities in porous basalt, andesite and rhyolite formations, and inflow and outflow channels develop. Agates contain 2 or 3 bands, deposited repeatedly as follows:

1. Globular chalcedony (cryptocrystalline), a hydrated, transparent polymer, which forms a plastic gel or polymer before crystallizing and is the first layer in an agate, also called length-fast chalcedony. This first layer coats the cavity and can host bacterial growth. When it crystallizes it is perpendicular to the C-axis and is also called length-fast chalcedony
2. Fibrous chalcedony (microcrystalline), anhydrous and white, crystallized as a rigid layer parallel to the C-axis directly from the diluted solution, and is also called quartzine or length-slow chalcedony
3. Euhedral quartz (crystals), a final stage if present which forms after dilution events

The cycle of deposition depends on seasonal changes in the water table. The gel which becomes the first layer of agate can have new layers added every season and thus stay in a gel state for a long time. This means the gel can host the growth of microbial communities for long periods and support them so that they do not collapse as they grow. That’s all on the very complex chemistry of gels, polymers, colloids, and crystallizing chalcedony. There is more information available in Campos-Venuti’s books and many other sources.

This all makes sense to me because I have seen waterline agates with plumes where a few plumes poke out into the empty cavity above the waterline. Also, the botryoidal features on the surfaces of some agates are actually the heads of plumes. I have collected small desert roses – chalcedony concretions – on the surface in the Davis Mountains which seem to be very recent creations. I have also spoken to people who have cut thundereggs and reported that where they would expect solid chalcedony, there is a rubbery not-quite-solid substance. Chalcedony that is not quite crystallized?

The fascinating aspect of all this is that eventually the chalcedony does solidify, and it preserves the detail of the formerly living microbial colonies, which can be grouped by their geometry as laminate, dendritic, lumpy or reniform, flames and plumes.

The inclusions in agate of biotic origin or mosses can be:

1. Filamentous: formed by bacteria arrange in long filaments
2. Lumpy: irregular or variable or dendritic
3. Spheroidal or cocci: little dots which can be suspended or group at the bottom

These types correspond to the three types of bacteria in multicellular microcolonies (Shapiro, 1988). Some are “benthic”, starting from the wall of the cavity and some are “planktonic” and float in the gel. These aggregations create complex colonial structures such as:

1. Laminated: microbial carpets, usually horizontal, sometimes domed
2. Dendritic: branching shapes
3. Lumpy or reniform: spheroid, not banded
4. Flame: microbial carpets with pinnacles
5. Plume: Similar to dendritic but larger and coarser

Colors are variable and depend on metal ions such as iron (red, yellow and green) manganese (black, brown and purple) and aluminum (white). Goethite, psilomelane, copper and pyrite may be precipitated as part of the structures.

Finally, Marco Campos-Venuti was a dealer at mineral shows as “Gems in Gems” (a great way to support your hobby) and often spoke with enthusiastic collectors about dendritic and other forms in agates who asked, “Is this a fossil?” “No” replied Campos-Venuti, quoting textbook geology, “It may look like a fossil, but it is a pseudofossil, a mineral that crystallized in that form.”. As he began studying inclusions in agates – and got hooked – he realized he was giving a rote, textbook answer on a poorly researched subject. Now he is the one telling these people that perhaps they were right all along.

References:

Banded Agates: A Genetic Approach by Marco Campos-Venuti

Genesis and Classification of Agates and Jaspers: A New Theory, by Marco Campos-Venuti

Biominerals: Microbial Life in Agates and other Minerals, by Marco Campos-Venuti (2022)

https://en.wikipedia.org/wiki/Hydrothermal_vent

https://en.wikipedia.org/wiki/Archaea

https://en.wikipedia.org/wiki/Extremophile

https://en.wikipedia.org/wiki/Three-domain_system

https://en.wikipedia.org/wiki/Stromatolite

https://en.wikipedia.org/wiki/Microbialite

https://en.wikipedia.org/wiki/Deep_biosphere

https://www.agatesandjaspers.com/product/biominerals/

Wikipedia:
A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Colloids include gels.

Phylogenetic tree of life based on rRNA data as proposed by Carl Woese et al. in 1990, with the hypothetical LUCA or Last Universal Common Ancestor.

Photographs:

by Steve Blyskal (so marked)

by Sigrid Stewart (not marked)

Have a GREAT INDEPENDENCE DAY celebration on the 4TH OF JULY!

SANDING  DISKS

One of the flexshaft tools that saves so much time is the snap-on sanding disk.  I mainly use the medium and fine grits but sometimes like the very fine ones that are sold for working with platinum.

Ordinarily, you’d think of placing the disk on the mandrel with the grit side facing away from your hand, but notice that you end up with your elbow up in the air.  Instead, try flipping the disk so that the grit side is towards your hand. It’s a much more comfortable position because the elbow is down near your side, and it lets me hold the work up close where I have a better view of what I’m sanding.

I use these snap-on disks so frequently that I keep multiple mandrels with different grits already mounted in the bur stand. Some mandrels have the grit facing out and some facing in.

Making jewelry involves a multitude of skills, intricate hand work, and a lot of problem solving. In this series Books in this series help to::

• Broaden your metalworking skills
• Improve productivity at the bench
• Save money on tools and supplies

Michigan Rocks! A Guide to Geologic Sites in the Great Lakes States by Paul Brandes is another marvelous field guide published by Mountain Press. It is a title every Rockhound in the Great Lakes State and any avid rockhound should have in their library.

The author begins with a brief overview of Michigan geology, complete with a geologic timescale, photos, and colorful illustrations. The overview is followed by descriptions of fifty-six geologic sites found in both Upper and Lower Michigan. Each site is carefully explained and complete with photographs, beautifully detailed illustrations, and complete driving directions illustrated with a map.  Following the site descriptions is a Glossary to help with terms the reader may not be familiar with, a list of further reading and internet resources, and the index. All of which contribute to the usefulness of this excellent geologic guide to Michigan.