North Brisbane Lapidary Club

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COVID-19 Update

Until the 1.5m social distance restrictions are relaxed numbers attending the club will be restricted, therefore bookings are essential. 

Beginners Day March 2021

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March saw another very successful beginners day, once again with some very promising new members.  Below are the responses from the day and photos of their work.

What did you enjoy most?

  • Everything we were shown was great
  • Good company while learning to work with metals. The sawing was quite enjoyable as well as the soldering
  • Finishing a custom made piece to even wear home

What did you enjoy least?

  • The course ending
  • Trying to get scratches out of the silver ring, but it is a good learning experience
  • What did you enjoy least?

Use one word or a short statement to describe the day

  • Great
  • Fun
  • Fascinating. Informative. Friendly. Helpful

Additional feedback

  • It would be great to learn more about the possibilities of what can be done with silversmithing at the club
  • Very comfortable environment and will feel welcome to return as soon as allowed

Flat Lap – New Equipment Available

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The engineers trust of Peter Smith, Tom Power and Barry Kirkham have been at it again and have rebuilt the old flat lap machine from a wooden framed truck tyre based machine into a new shiny stainless steel “smicko” machine.  Stainless steel has been used on all of our work surfaces now to make maintenance and cleaning easier for members.

A flat lap is available to make polished faces on larger rocks like the one shown in this photo.

Using the 150mm diamond wheels for any stone larger than about 50mm is not permitted in the club.  The reason for this is that it causes excessive wear on the diamond wheels which are expensive, and on a technical level, it is not possible to get a perfectly flat surface on a curved wheel.  The only way to achieve this is either manually on a piece of glass or using the flat lap.

There are several laps provided with the machine, but all grinding from coarse through to prepolish are achieved using a rotating steel disk to which an appropriate grade of silicon carbide grit is added.  Water is dribbled onto the disk to make a slurry and then the rock is held firmly against the steel disk with the silicon carbide being an abrasive element to the task.  As the rock face is flattened, finer and finer grades (from 80, 200, 400, 600 up to 1,200 grade) are used to get rid of all scratches and defects on the surface of the rock.  Important! Between each grade of grit the steel disk and the rock need to be thoroughly washed to remove all traces of the coarser grit.

Once grinding has been completed and everything washed thoroughly, the polishing process can be commenced. For prepolish, a copper lap is provided which should be used with 3,000 diamond paste.

To polish,  a leather faced lap  is fitted, to which a damp slurry of tin oxide is added to this lap to complete the polishing process.

Peter has provided a user manual, with which members should be familiar before using the machine.

When next in the club, have a look at this machine, adjacent to the saw room.

A big thank you to  Peter, Tom and Barry for their efforts in providing top quality machinery for club members to use.

More Pendants

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by Mary

Just playing with what I have available!  The last pendant is an amethyst cabochon.

Materials

  • Silver plate (0.8mm thick)
  • Piece of silver for bail
  • Bezel (own choice)
  • Cabochon (own choice)

Steps

  • Measure and cut piece of silver plate, file and smooth edges and corners.
  • Add some design or stamping if desired. Stamp pendant back with ‘925’.
  • Cut a strip of silver for the bail, file and smooth edges. Anneal. Fold to form bail.

 (Consider bail size and the chain width to flow through it).

  • Using flat nose pliers to flatten and close bail ends ready for soldering. Apply flux and solder pieces to bail, and apply heat/solder.
  • Position the bail onto the centre back of the pendant.  Apply flux and solder pieces. Solder applying heat to top side of pendant.
  • Wrap bezel around the cabochon, mark bezel. Check length and cut. (Allow a little extra, adjustments can be made as you fit it tightly around cabochon).
  • Match bezel ends, place solder pieces around inside of shaped bezel. Apply heat on the outside of bezel, watch it flow. Reshape bezel and fit cabochon inside it. Check height of bezel. If bezel is too high file some off the bottom.
  • Position bezel on the pendant plate, ensuring it sits flat/flush.
  • Apply flux and solder pieces to the inside of the bezel. Apply heat around the outside and watch solder flow. Check bezel has totally attached to the pendant plate.
  • Clean and polish pendant. Put cabochon into bezel, ensuring it sits in evenly.
  • Using square end pusher tool, start to fold bezel over the cabochon, start at top and bottom, then each side (NSEW) evenly. Then carefully fold remaining bezel onto cabochon. Can use a burnisher tool to ensure bezel sits firmly onto the cabochon.
  • Give final clean and polish.

Square End Pusher
Burnisher

Pendants

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by Mary Lancaster        

Looking for a different activity, I found these cabochons in my stash and decided to have a go at making a pendant (first time!). The first one was a bit of a challenge, however trial and error resulted in the above. Maybe next time I can try using silver plate for the backing.       

 

Learning to Cab

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Always good to see members trying their hand at a new skill with great results.  We recently had a Friday night work session with Thierry instructing some members new to cabbing.

Petrified Wood

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by (Woodworm) Christoph

Here are some things about petrified wood which get me excited..... well, not just wood, all permineralised plant material.

It all started in Germany where I was born in the town of Chemnitz, world famous for its Permian petrified forest and the local museum specialising in petrified wood from around the world and particularly in Permian flora.

As a child I always loved going into the Museum für Naturkunde Chemnitz. I was amazed by the fine detail of preservation right down into the cell structure. An ancient plant turned into rock. As I grew up I met a few collectors, called wood worms, and I was hooked even more. We went on field trips all over Europe and I still have a large collection over in Germany at my parents place.

Now how does petrified wood form?

Most importantly is that the wood is covered and locked away from oxygen, so it can't rot away. In many cases petrified forests are links to volcanic activity. If things go right there is an eruption, which produces mostly ash and this ash will bury the forest. Over millions of years, minerals, predominantly quartz with other trace elements and metals will slowly impregnate the cell structure turning the wood into stone. This process is still not fully resolved.

The other way is wood gets buried by sediments such as sand. The process is the same, key is the presence of enough minerals to impregnate the wood. There have been cases that animal traces such as toredo borers (known as the famous peanut wood from the Kennedy ranges) or termites with their excrements (coprolites) have left their traces.

I'm more interested from a scientific angle of what species grew at which time, and how they have evolved through the evolution.

Petrified wood can actually be found on every continent. Yes, even Antarctica which was part of the super continent Gondwana.

There are some very famous petrified forests in the world such as the one in Arizona with its beautiful red petrified wood.

Or most exciting Araucaria cones from Argentina.

There is so much unknown still and only recently I have found a species of fern? which I haven't found in the literature yet.

Australia has got a good diversity to offer from the Permian deposits in the Bowen basin to the well sought after Jurassic woods, Donpoxylon and ferns from central Queensland around Miles and Chinchilla and Lune River in Tasmania. Cretaceous peanut wood from WA and more recent tertiary opalisiert woods from Springsure. There are many more places to find it.

A good tip is the display in the Miles historical village. It houses the collection of former Norman Donpon, a mad collector which I was privileged to meet a few years ago.

Now I could go on and on about it .....

Below are a few more pieces from my collection.

Do you know Mohs?

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by Katarina

Mohs - Carl Friedrich Christian - was an old German fella, a geologist and mineralogist. He lived some time ago (1773 – 1839). You wonder why I mention Mohs? Well, he expanded on the knowledge from Theophrastus and Pliny the Elder who determined that Diamonds where pretty hard compared with other minerals such as Quartz.

Good old Carl used the knowledge from those who came before him and it became the basis of the hardness scale he developed, today known as Mohs’ Scale of (Mineral) Hardness.

When Mohs developed his hardness scale in 1812, very little information about mineral hardness was available. He simply selected ten minerals that varied in hardness and arbitrarily placed them on an integer scale from 1 to 10. It was a relative scale in which a mineral of unknown hardness could be tested against a group of ten index minerals to see where it positioned on the scale.

You most certainly have heard talk around the club house of how hard a piece of rock / mineral / gemstone is when people want to polish them.

This hardness is actually measured by the Mohs Scale of Hardness. The scale measures the scratch resistance of minerals, how difficult it is to scratch a specific mineral. This has an impact on how difficult it is to polish one of our pieces into a beautiful cabochon or faceted stone.

The highest resistance to scratches is found on diamonds and they have been assigned the hardness 10. The least resistance to scratches is talc – it basically scratches itself – and it therefore has the hardness of 1.

The higher a mineral is on the scale, the harder it is to polish. And the reverse works of course too, the lower the ranking, the easier it is. Which of course means you could polish a low ranking mineral away to nothing in no time.

A good indicator to how hard a mineral might be is sawing a piece. The more the saw has to work, the harder it usually is.

But all in all, the scale doesn’t mean much. After all, what does it mean for example, that an Amethyst has the hardness 7 if you have nothing to compare it with? The numbers on the scale are just that, numbers.

So I have searched the net and asked my friend Google if there are any examples for the hardness. And as Google knows everything, it has delivered. The combined findings are in the table.

One of the comments that I remember is that Stones with hardness of under 4 may not polish at all or will only take a light shine. Most of the stones hobbyists polish are found in the 6 to 7 range.

As you will see in the table, many minerals don’t have a specific hardness but rather sit on a sliding scale, depending on the composition of the minerals.

And if you ever find yourself in Vienna, why not look for the memorial plaque in honour of Carl Mohs.

Sources:

https://www.gemsociety.org/article/select-gems-ordered-mohs-hardness/ - here you will find a more complete list of minerals and there hardness according to Mohs

https://geology.com/minerals/mohs-hardness-scale.shtml - more in depth information. Including how to test minerals.

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

https://www.britannica.com/science/Mohs-hardness

So You Want to….

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Buy a Head Loupe

by Ray Wilson

A magnifying head loupe is one of the most useful tools that you will buy when you commence your journey in lapidary or metalsmithing.  A head loupe gives you improved vision of your work, showing up those annoying scratches that you thought were sanded out.  A head loupe gives you the magnification necessary to see your work but leaves you with 2 hands free to hold and manipulate your work.

Head loupes need to be adjustable to fit different size heads and all models should come standard with this feature.  The more substantial loupes will come with a knurled nut that is wound in or out to adjust the plastic head band.  Some of the cheaper types will have Velcro straps that can be adjusted to the correct head size.  Loupes typically will also move up and down to allow the user to lift the loupe away from the eyes when not in use.  A nice feature that means you don’t have to take your loupe off of your head when not in use. Headbands can be plastic or leather covered.  Leather bands are useful as a sweat band if working in the glare of strong lights or a hot soldering torch.

Loupes also come with different type of lenses and in different shapes.  The more expensive varieties will have optical glass whereas the cheaper option will have acrylic lenses.  Glass lenses are an advantage as they will not scratch as easy as the plastic ones.

Each manufacturer will decide what level of magnification to offer in the lens.  Standard loupes will have a magnification of around 2.5X (2.5 times).  With some brands, additional lenses of increased magnification are included and can be simply replaced by undoing a couple of threaded bolts.  Remember that with each increasing level of magnification the focal point comes closer to your face.  For example the commonly used Optivisor with a 2.5X lens has a focal length of around 200mm.  A 3.5X lens has a focal length of 100mm.

Other features are also available from some manufacturers like an additional lens for one eye, effectively doubling the magnification for that lens.  Often a light is also included.

Donegan Optivisor – Rio Grande

For many years the only head loupe in the market was a Donegan head loupe made in USA.  These loupes are still the standard in head loupes and you will never go wrong buying a Donegan Optivisor.  Recently though the weakening Australian dollar has meant that this loupe now retails for about $120 in Australia.  Recently, like so many other tools, “knock offs” or copies, that are made in China, have appeared on the market.  To all intents and purposes, they are an exact copy of an Optivisor in both design and functionality.  In the favour of the copy is the price.  These can be purchased in Australia for around $60 and come packaged with 4 different lenses.  With Optivisor only 1 lens is provided but others can be purchased as required.  If this is still too much for you a copy of the acrylic head loupe with Velcro straps is available for about $20.

Other models can be purchased from places like Kogan or Jaycar.

Tiltable LED Headband – Kogan              LED Headband Loupe – Jaycar

Head Loupe with 4 Glass lenses – Gemcuts

A good head loupe will last a long time.  I have just replaced my original Optivisor bought in 1998.   After weighing up the options I went for the Chinese knock off from Gemcuts.  I can’t fault it and at $60 including 4 optical glass lenses is a great option for my failing eyesight.  Given that this investment will last you a long time, buy the best that you can afford at the time.