Lapidary Terms Explained: Cabochon

This post is the second in a series of explaining terms used in the lapidary world (the first being around the Mohs Hardness Scale). I thought I would go right back to the basics for this one and explain the word Cabochon.

The term 'Cabochon' originates from the Middle French word caboche meaning 'Head'.

A cabochon is a gemstone, generally a semi precious stone, which has been cut, shaped and polished by a Lapidary into a convex or domed stone with a flat back.

Free Form Designer Cabochons; Left to right they are Picture Jasper, Boulder Opal, Chrysoprase and Green Jasper

Cutting a gemstone to cabochon form is usually a way to cut material that is opaque, as opposed to faceting a translucent stone. In general terms, hardness of a given stone is also taken into account with material rating greater than 7 on the Mohs Hardness Scale being reserved for faceting, rather than cabochon cutting.


Free Form Cabochons in Jewellery; Left to right they are Green Serpentine, Kyanite, Boulder Opal,
Agate and Dendritic Chalecedony

It is widely accepted that their are essentially 2 forms of cabochons; Standard cabochons and free form (or 'designer') cabochons.

Standard 30mm x 40mm Oval Cabochons; Left to right they are Petrified Wood, Jasperlite, Banded Chert and Agate

A standard cabochon is a stone which has been cut into a 'standard' shape such as an oval (as pictured above), square or circle whereas a free form or designer cabochon is a stone cut into an unusual shape without the use of a template. Generally designer cabochons have been designed to take full advantage of what the material has to offer visually, or to allow the cutter some artistic licence with the stone at hand. Cutting a stone cabochon generally involves Diamond wheels (both Metal and resin bonded) or Silicon Carbide wheels, although Diamond has become the preferred method. You can view my How To Guide on cutting stone cabochons by clicking here.

Until next time!

Marble Bar Jasper - A beuatiful but hard to come by material

Marble Bar Jasper is a form of very fine grained silica found just outside the small outback town of Marble Bar, the town taking its name from the now famous 'jasper'.

Marble Bar Western Australia - Located south east of Port Hedland approximately 200km from the Great Northern Highway

The area was first colonized when gold was discovered. The 'Bar', as it is locally known was originally mistaken for marble and for the fact that it blocked the flow of the Coongan River.

The 'Bar' - Marble Bar Western Australia - Photo courtesy of 'The Grateful Dad' on Flickr

The jasper, or more accurately the fine grained silica, is a magnificent mix of red, white and blue/black striped rock. The colours in the stone are as a result of inclusions of mineral impurities such as iron ore causing the red (more commonly known as Hematite), pyrites and carbonaceous matter creating the blue/black tones. The white areas of the stone are more 'pure' forms of silica.

As it is now illegal to fossick and remove the material, doing so carrying a $10,000 fine, it is not unheard of to come across 'old stock' every now and again. The rough shown here was found at the recent Gemkhana show in Albury - I couldn't walk past it! In addition to the material shown here, I am also lucky enough to have a small supply of slabs which my Grandfather collected many many years ago.

Marble Bar Jasper Pendant - $40

Although this material is a jasper, forming part of the quartz family, I have always found it to be quite a bit softer than most other Jasper's that I have cut. In saying this, it still finished with a great shine/polish, and the patterns can be spectacular. You can see in the piece shown here how the stone has fractured, shifted and then re healed to form a very interesting piece of rock.

Marble Bar Jasper Pendant - $30

Marble Bar Jasper Pendant - $30

These two pieces also show the colour variations which are evident within the material.

Swiss Army Knife with Marble Bar Jasper Scales

All in all, Marble Bar Jasper is a beautiful and unique piece of natural geology which is admired by many. Unfortunately not all will have the pleasure of cutting this material, but leaving the natural environment of its origins intact is probably more important. I am one of the lucky ones!

Until next time!

Lapidary Terms Explained: Mohs Scale of Mineral Hardness

Since starting this blog in November last year, I have discussed a number of gemstones and minerals from both a chemical/scientific point of view and from a lapidary point of view. Throughout many of these posts, I have referred to the 'Mohs Scale' or 'Mohs Scale of Mineral Hardness' when discussing the hardness of a given gemstone. As such, I thought it prudent to clarify what the 'Mohs Scale' actually is!

Mohs Scale of Hardness: Image
courtesy of www.thegemchronicles.com

The Mohs Scale (also knowns as the Mohs Hardness Scale or Mohs Scale of Hardness) was developed by the German geologist Friedrich Mohs in 1812 and is widely used by lapidaries to describe the hardness of a given mineral or gemstone. Diamond was, at the time, the hardest material known to exist so is at the top of the list, with Talc being at the bottom.

(Check out this article from newscientist.com for an interesting read on the hardest material known to man)

  

Essentially what the Mohs scale does is describe the scratch resistance of a given material compared to other minerals. To simplify this, referring to the above table, gypsum will scratch talc therefor gypsum is harder than talc. Likewise corundum (sapphire, ruby etc) will be scratched by diamond so is therefor softer.

To find the Mohs classification of a particular gemstone or mineral one needs to find the softest material that will be scratched by the given gemstone, or find the hardest material that will be scratch by the given gemstone. The gemstone is then given a relative number.

To give an example of this, steel will (in general terms) scratch Fluorite, but will be scratched by Apatite, giving steel a Mohs rating of 4 - 4.5

The scale does not refer to the relative hardness of a given material, ie. Corundum is twice as hard as Topaz, but diamond is 4 times harder than corundum. The table below (courtesy of Wikipedia) shows this with the additional column titled 'Abosulte Hardness'.

Mohs Hardness Scale with additional column
titled 'Absolute Hardness'

So from now on, when I refer to the 'Mohs Hardness Scale' when discussing gemstones, you will know what I am on about! 

Feel free to also check out my How-To guide on cutting a stone cabochon and my tutorial on creating gemstone scales for Swiss Army Knives

And if you like the content of this blog, feel free to share!

Until next time!

Customised Victorinox Swiss Army Knives With Gemstone Scales

Customized Swiss Army Knives Complete with Stone Scales

It has been a long time coming, mainly because of my lack of organisational skills, but I have finally made available my first release of Customised Victorinox Swiss Army Knives complete with gemstone scales! You might remember my post from a while ago relating to the Swiss Army Knife that I put together for my Dad for Christmas late last year, in that I hinted that I might be making some available through our store in the future.

Customized Swiss Army Knives Complete with Stone Scales

Well I am excited to announce that I have finally been able to finish the first release of these customized knives, all be it only 3 pieces at this point! All 3 knives are the Victorinox Classic SD model and are in an 'As-New' used condition. Each piece is completed with handcrafted stone scales created by Jaka Gems. The material for each knife has been painstakingly selected taking care to avoid any cracks, pitting or other nasties so that each knife is a beautiful but functional piece. These 3 pieces will hopefully be the first of many to come!




Customized Swiss Army Knife with Greenstone Scales

This first piece (pictured above) has been finished with Greenstone originating from New South Wales (Australia). The material is a beautiful deep green with yellowing bands running diagonally across the scales. The finish is of a high shine and a magnificent example of this particular material. This piece is available for $70 through our store.

Customized Swiss Army Knife with Nundoorite Scales

Secondly, pictured above is a piece that has been finished with Nundoorite. Nundoorite is a material which originates from near Broken Hill in New South Wales, although Nundoorite is not a 'recognised' mineral name. The material is and Orthoclase Syenite with flecks of green Aegurine floating through. The material has finished with an excellent polish and has created an aesthetically pleasing pocket knife which will please even the serious collector! This piece is available through our store for $75



Customized Swiss Army Knife with Moss Agate Scales

Finally we have a knife finished with beautiful Moss Agate. I consider this piece to be the 'flagship' of this initial release - The Moss Agate is a beautiful white to translucent chalcedony with magnificent moss like inclusions of hornblende and chlorite. As is the case with most Agates/chalcedony's, the final polish on this piece is magnificent. This piece is available through our store for $80

If you would like to know more about these knives, feel free to contact me via our email address at jakagems@hotmail.com - you are also more than welcome to contact me to discuss customized knives should you want a particular stone. I am happy to discuss creating a piece similar to the above using a material of your choice.

Until next time!

Gemkhana Part 3

This is the 3rd and final installment of my posts relating to the Gemkhana event in Albury over the weekend of 9th and 10th March. See part 1 and part 2 by clicking on each. Here I will detail to last 4 pieces of material that I purchased which I will hopefully turn into some very nice pieces over the coming months.

This is a piece of Siltstone, although it was being sold as 'Zebra Stone' by the vendor on the day. My suspicion is that this sort of material is easier to sell when it is called 'Zebra Stone' given the popularity of that particular stone. Although zebra stone is a variety of siltstone, it has a far more distinctive pattern than this piece. In saying this, I loved the colour and uniform pattern of this slab of material so grabbed it anyway. I am not sure what I will do with this just yet as it is a very soft stone, but will see how we go!

This piece is Ribbon Jasper originating from New Zealand. Jasper is basically a variety of quartz and is quite a hard material. Because of makeup and hardness of jasper, it generally takes a magnificent shine and the variety of colours and patterns is endless. This particular piece caught my eye because of the pattern running across the stone. It has quite a few healed fractures that I may need to avoid, but the piece is large enough for this not to be too much of an issue.

This piece is Rhyolite which I am told originates from New South Wales (Australia). Rhyolite is also part of the quartz family and is generally a volcanic creation. It is worth noting that when the Rhyolite formation cools too quickly for crystals to form, instead of Rhyolite being the end result, Obsidian is formed in its place. I haven't cut rhyolite before so not quite sure what to expect. In saying this, if it is in the quartz family I would anticipate it to be quite hard and taken a good polish.

Last but not least we have a slice of unknown material. I was told that it originates from New Zealand but that was all the vendor could tell me. My thoughts are that it is some sort of agatised jasper or some other form of quartz. It certainly has that look and feel to it. I liked the pattern on it so thought I would grab it regardless and we will see how it cuts up!




Well, that's it as far as our Gemkhana adventures go for another year. I certainly had a great weekend and was very pleased with the turnout. The organisation of the event was well done and there were plenty of people through the gates. I am certainly looking forward to next years show! Remember that if you like the look of any of the materials I have posted from the show, feel free to drop me an email via jakagems@hotmail.com and I am sure we can work a piece out for you. Also don't forget to check us out on facebook and on storenvy.

Until next time!

Gemkhana 2013 Part 2

Following on from my post from the other day (view here), here are some more of the rough material that I got my hands on at the Gemkhana event in Albury.

This is a piece of Mahogany Obsidian. I have already explained obsidian in my post from the other day and the fact that it is a pain to cut, but again, I couldn't walk away from this as it comes up so nicely! This particular piece has quite interesting patterning though it.

Nundoorite (Pictured to the right) is a material that I had never seen or heard of before. From the little information I have found relating to this particular stone, I have been able to ascertain that the name 'Nundoorite' is as a result of where this material was originally found - Nundoora Station near Broken Hill (New South Wales). The original deposit of this stuff was mined out some 20 or 30 years ago, but further deposits of similar stones (such as this piece) have since been located nearby. This stone is mainly made up of orthoclase syenite with green flecks of aegerine running through. Quite an interesting looking stone and I am certainly intrigued as to what it will end up like.

These 3 slabs are a stone known as 'Sonora Sunrise' (or Sonora Sunset depending on who you talk to!). It is a relatively new find originating in Mexico and is a mixture of Cuprite (red) and Chrysocolla (green). I have been chasing some of this stuff for a while now so was pleased to find these slabs. It seems like quite a soft material so not sure how the final polish will end up.

These 3 are small slabs of 'Marble Bar Jasper' - a material originating from an area just outside the small West Australian settlement of Marble Bar. I have some of this at home already and have cut a few pieces out of it (this piece in particular came out very nicely!), but it is so hard to come by that I could not leave these pieces behind. The vendor did have a few other small slabs, but they were quite cracked and I didn't think I could do a lot with them. These pieces on the other hand looked fantastic.

This piece is a relatively large slab of Poppy Jasper from New South Wales. I quite liked the patterns across the stone, with small agatised areas amongst beautiful red jasper. Jasper is known for taking a brilliant shine and I have no doubt that this slab will not disappoint. I have a project in mind for this piece, so stay tuned!




I have 4 more slabs yet to show you from the material I bought at Gemkhana which I will post over the next couple of days, so swing back by my blog to find out what they are! Also keep an eye out both here and on my Facebook page for pieces created out of this rough material!

Until next time!

Gemkhana 2013

As some of you may be aware, Jaka Gems attended the 2013 Gemkhana Show in Albury of the weekend of March 9th and 10th. Gemkhana is Victoria's state level Gem and Mineral show which was this year presented by the Albury Lapidary and Allied Crafts Club in association with the Victorian Gem Clubs Association

Both organisations did a fantastic job with the running of the show with plenty of people coming through the gates.

  

The Jaka Gems stall was positioned in the outdoor area and the Albury weather certainly putting on a show for all - Temperatures in the high 30's on both days ensured that plenty of water was consumed as well as plenty of sunscreen! Finding shade was probably the most difficult task for the weekend with our small pavilion moved several times chasing that elusive piece of dirt out of the sunshine!

We purchased quite a bit of rough material over the weekend, which I will show you some of in this blog entry. The picture to the right is a slab of Kambaba Jasper. I have been wanting to get some of this material for a while and was really happy to find this very detailed slice. Kambaba Jasper is a material originating from Africa and is basically fossilised algae. I have seen some cabochons of this stuff and it takes a magnificent shine, but I am far more excited about the interesting patterns in it. I had a project in mind for this piece when I bought it, but it has turned out that the slice is just a little bit too small for what I wanted. Despite this, I am still pretty happy with the purchase!

This next slab (to the left) is a piece of Rainbow Obsidian. I was simply unable to walk past it! Obsidian is a pain to cut, but finishes really well and the pattern and colour on this particular piece is amazing! Obsidian is essentially a naturally occurring glass which is created by rapidly cooling lava flows. When the lava cools quickly, it does not create crystal growth and obsidian is the result.

The material to the right is a slice of Rubies in Fuschite. My wife saw a cabochon of this material at another stall and then demanded that I get some to cut her some pieces! The material generally originates from Southern India and contains rubies (which can range in colour from pink to bright red) encased in the bright green Fuschite.

Keep an eye out on our facebook page and store for pieces cut from these materials. I will also be posting more of our buys on this blog over the coming days so definitely keep on checking back in here for more and don't forget to share with your friends! If any of the material here interests you, drop me a line either on facebook, or via email at jakagems@hotmail.com - I am more than happy to discuss customised pieces!

Until next time!

New Opal Products Available

Some time ago I called for some expressions of interest for some opal triplet jewellery. I got some fairly positive feedback in relation to this expression of interest so I decided to go ahead and order some settings. They arrived yesterday so I was busy last night setting the triplets into the settings! They have all been uploaded into the store today!

4mm round opal triplet stud earrings

The first product is the 4mm round triplets set into sterling silver stud settings. An example of these is pictured to the left, and their are 4 sets available. I have been able to keep the price down to $12 per set.

5mm round opal triplet stud earrings

The second product is the 5mm round triplets set into sterling silver stud settings. An example of these is pictured to the right, and their are 6 sets available. I have been able to keep the price down to $15 per set.

6mm x 4mm Opal Triplet Earrings

The third product is the 6mm x 4mm triplets set into sterling silver kidney wire settings. An example of these is pictured to the left, and their are 5 sets available. I have been able to keep the price down to $15 per set.

7mm x 5mm Opal Triplet Earrings

And last, but by no means least, the flagship product of this particular release is the 7mm x 5mm triplets set into sterling silver kidney wire settings. An example of the is pictured to the right, and there are 5 sets of these available. I have been able to keep the price down to a low $20 per set.




I am hoping that these pieces will be successful, if they do turn out to be popular I will definitely be doing more releases, and perhaps even adding to the range. Keep an eye on my Facebook page for updates in relation to this!

Until next time!

Chalcedony

 

Free Form Designer Agate Cabochon

Chalcedony is a mineral made up mostly of Silicon Dioxide and is a cryptocrystalline variety of quartz. Chalcedony comes in many forms and is essentially a term for a group of semi precious gemstones, rather than a single stone. Chalcedony and its variants are considered among the most beautiful stones in the world and have a hardness rating of generally between 6.5 and 7 on the Mohs Hardness Scale.



Free Form Designer Chrysoprase Cabochon

The name 'Chalcedony' comes from the Latin word chalcedonius. However it is also believed that the original Latin word and the current usage of the name 'Chalecdony' derive from an ancient Greek settlement in Asia Minor. This settlement was originally known as Chalkedon, but the modern English interpretation of the settlement is Chalcedon - hence the spelling of the name 'Chalcedony'.  

 

Free Form Designer Agate Cabochon

 

This particular gemstone group has been used as long as humans have been utilising their surrounding materials. Some of the earliest and most primitive human tools that have been discovered have been made of various types of Chalcedony.

Chalcedonies are found in an immense array of colours including, black, blue, brown, colorless, gray, green, orange, red, violet, white, yellow, or any combination of these. 

Green Chalcedony with Minor Dendrites

 

Because of the vast array of varieties, the use of chalcedony eventually extended to that of decorative items. Native Americans for instance believe Chalcedony to be a sacred stone and it is used for ceremonial purposes. They believe that Chalcedony promotes stability within each tribe.

  

35mm x 18mm Heliotrope (Bloodstone)
Cabochon

As stated above, Chalcedony is essentially a term used to describe a broader group of gemstones which varies widely in colour and appearance. The most notable members of this group include gemstones such as Agate, Carnelian, Heliotrope (Bloodstone), Chrysoprase, Aventurine and Onyx, but has many other members as well. Chalcedony deposits in its various forms are found worldwide, with particular areas being known for or associated with the individual forms of chalcedony.

From a Lapidary Point of View
Because of the endless range of chalcedony forms, this particular stone is always going to please. From the Banding of Agates, through to the rich apple green of chrysoprase, to the spotted nature of Heliotrope, there is always going to be something of interest in a Lapidary sense. Some of the most eye catching and beautiful cabochons that I have cut have been some form of chalcedony or another. Most chalcedonies are at the harder end of the scale (with a Mohs rating of generally 6.5 to 7) and the compact crystalline structure of the material results in a beautiful mirror like finish. It is not surprising then that most lapidaries are more than happy to cut this material, and I am certainly no exception.

Free Form Designer Banded Agate Cabochon

Thanks for checking out my blog and certainly feel free to share with your friends. Remember, all of the pieces presented in this article have been cut by me and most are available for purchase (along with plenty of others!). Also don't forgot check us out on Facebook to keep up with all of our updates!

Until next time!

Tiger Eye

Tiger Eye Rough - Image Courtesy of www.crystalsrocksandgems.com

Tiger Eye (or Hawks eye as the blue variety is known), a member of the quartz family, gets its chatoyant  nature (a cats eye type effect) as a result of its crocidolite content. Crocidolite is a mineral which is essentially fossilized asbestos fibres and is a blue colour.

African Tiger Eye Pendant - $30

How does Tiger Eye Form?
Tiger Eye is a member of the quartz family. It begins as blue mineral called crocidolite (Asbestos). This blue mineral is made up of iron and sodium components. The formation of Tiger Eye begins when quartz slowly replaces the crocidolite over time. The quartz embeds itself between the fibrous material. Once the process is completed, the resulting stone is either a golden brown (Tiger Eye) or a brilliant shimmering blue (Hawks Eye). As the stone forms, the iron and sodium content is completed removed. The replacing quartz takes on the same fibrous structure of the original material giving the stone its parallel lines. Because of the crystaline nature of the quartz, the movement of lights across the stone and its luster results. It is this property that makes tiger eye so popular and sort after.

African Tiger Eye Pendant - $45

What gives Tiger Eye its colour?
Although quartz replaces the iron and sodium content during the formation of the stone, trace amounts of iron oxide and other inclusions remain within the material. These trace amounts embed themselves between the remaining crocidolite and quartz. This composiyion creates the yellows and golden browns that are common in the stone. The blue Hawks Eye is a more 'pure' form of the stone having little inclusions remain but is rarer than the more common yellow. The third form of tiger eye, being red tiger eye, does not occur naturally. It comes about by heat treating tiger eye.

West Australian Tiger Eye Pendant - $20

Where Does Tiger Eye Occur?
The largest deposits of Tiger Eye are generally found in Africa, particularly South Africa and Namibia. Other deposits of this gemstone occur in Australia (particularly Western Australia), Burma, India, United States, Brazil, Canada, China, Korea and Spain. 

Tiger Iron
Tiger Iron is another common form of Tiger Eye which occurs mainly in South Africa and Western Australia. Tiger Iron is a banded gemstone comprising of lineal bands of Tiger Eye, Red Jasper and Black Hematite.
 

West Australian Tiger Iron Pendant - Custom made pendant

Lapidary Point of View
From a lapidary point of view, Tiger Eye is fantastic to cut. It is relatively hard measuring 6.5 to 7 on the Mohs hardness scale (some of the iron stone surrounding tiger eye can be a lot harder). In saying this, it can be somewhat frustrating at times as there is often differences in hardness between layers/bands which can cause a endless undercutting - something that can be very irritating. I have started plenty of Tiger Eye cabochons that have been discarded half way through as a result of this. The final product comes up with a magnificent shine with a beautiful chatoyant/lustres finish - This is what keeps me coming back to cutting the stuff!

All the pendants in this article have been cut by Jaka Gems. I am happy to consider custom orders of this gemstone as I currently have a reasonable supply of rough. Thanks for reading my blog! I would love for you to share this, or other articles on this blog, so feel free!

Until next time!

Custom Piece - Blue Lace Agate Earrings

I had a customer contact me late last week asking if I could put together a particular item for her.  She had seen the Rhodochrosite pendant and earring set I recently did and quite liked it, particularly the earrings. 

Rhodochrosite and Sterling Silver
Pendant and Earring Set

She asked me if it were possible to make a set of earrings similar to the rhodochrosite ones, but with blue lace agate as she preferred the colour of the Agate. The agate has a very similar pattern to that of the rhodochrosite, but with a nice light blue colour.

The result is a custom made set of Blue Lace Agate cabochons measuring 10mm round each. Each cabochon has been set into Sterling Silver Bezel setting earrings in a Kidney Wire style. This has made a very simple but attractive set.

Custom Made Blue Lace Agate and Sterling Silver Earrings

Blue Lace Agate is a fairly common form of agate which is a form of chalcedony. Blue lace agate was originally discovered in Namibia, which today is still the main source of the gemstone, although South Africa also has a large deposit. In the past, blue lace agate has also been known as the 'Gem of Ecology' because of its blue and white banding, which can quite often look like clouds in the sky. The material is great to cut, it is relatively hard (Blue lace agate rates approximately 6.5 - 7 on the Mohs hardness scale) and finishes with a magnificent shine.

 

Blue Lace Agate Cabochon on
Leather Cord Necklace

The earrings are hopefully being delivered today. I hope my customer enjoys them as much as I enjoyed making them! I am more than happy to consider most custom orders - If I am able to source the material, I should be able to cut it for you. You can contact me via email (jakagems@hotmail.com) or via my facebook page if you want to discuss a custom order.

Until next time!

What is Opal?



Coober Pedy Jelly Opal - $90

Opal is one of the most popular stones in the world today. Its colour variations can be spectacular with bright reds, blues, greens, purples and everything in between. But what is opal and how does it occur? What process creates these brilliant colours that we see?

Boulder Opal Pendant & Earring Set - $125

One of the ways science defines a mineral is that which has a crystalline structure; Opal does not have such a structure, however it is generally referred to as a mineral. Despite this, Opal is in fact a 'Mineraloid' which is essentially a term that describes a geological substance which is lacking in a crystalline structure. Most mineraloids are still referred to as 'minerals' even though this is not strictly the case.

Queensland Boulder Opal Pendant - $95

Opals colour was a mystery for quite some time, with many theories being put forward in the early days. It wasn't until the 1960's, with the invention of the electron microscope, that it was discovered that opal was made of up of billions of tiny silica spheres all arranged in an orderly fashion. These spheres are roughly between, in the case of precious opal, 150 to 400 nanometers in diameter. This collection of silica spheres is formed via water mixed with silicon dioxide making its way through cracks and voids in the earths surface. Most of the water then evaporates (opal does have a small water content) leaving behind the tiny silica spheres. It is said that it takes some 4 million years for 1 centimetre of opal to form at a 45 metre depth.

Queensland Boulder Opal Cabochon - $295

The tiny spheres that make up the stone then diffract the light that enters the stone and divides it into the spectral colours. The colour shown is dependant on the size and arrangement of the tiny silica spheres present within the stone, and the colour patterns changes with the angle of the piece. If the spheres become too compact or unaligned, then the light will run straight through, without diffracting, creating opal with no colour play (this is commonly known as 'potch' or 'common opal').

Boulder Opal Pendant - $65

Coober Pedy Jelly Opal - $150

Pure opal is generally colorless, with impurities giving each piece its background colour. black opal, and opal with an orangey look to it have Iron, manganese oxides and organic carbon impurities giving them their background colour, whereas 'milky' or 'jelly' opal (such as that common in Coober Pedy) has tiny air pockets within the stone.

Coober Pedy Jelly Opal - $90

It is interesting to note that 97% of the worlds opal is mined in Australia with 80% of that coming from the mines of South Australia including Coober Pedy, Andamooka and Mintabie. Other opal deposits around the world can be found in the US (Particularly Nevada), Czech Republic, Slovakia, Hungary, Turkey, Indonesia, Brazil , Honduras, Guatemala, Nicaragua and Ethiopia. In an amazing announcement back in 2008, NASA also indicated that there were opal deposits found on Mars!

From a personal point of view, opal is one of my favourite stones to cut, although certainly comes with its own difficulties which can be somewhat frustrating. The colour play can quite often only be found within thin bands running through the material. Given the soft nature of the stone, this can quite often result in cutters grinding away too much material looking for better colour and ending up with no colour at all! This alone has proved enough to make a lot of people shy away from cutting a good bit of opal. My suggestion for those just starting out is to try your hand with some potch first, before going for the good stuff. At least this can give the cutter some sort of idea of how the stone runs across your grinding wheels and can give you a 'feel' for the material. The end result of a well cut opal can be stunning and makes the frustrating nature of the stone very much worthwhile!

I have put up photos of a few of my opals on this post, but you can see more of my work with this amazing material by checking out my store here. Until next time!