Sorting Boulder Opal
No shortcuts in life
There are no shortcuts in life when it comes to handling boulder opal.
From the moment we go to the mine, to pick up the opal bearing rocks and load into the 3 x 200 litre (44 gal) drums strapped onto the back of the truck, to the moment we photograph the opal to list on our webstore, an opal will be handled numerous times.
At every stage of the process, from the mine to the finished product, decisions are made on whether to process the raw boulder opal it into a variety of cut and polished products or leave it as rough to sell as individual pieces, or rough parcels.
The rough is sorted into potential gem grade (cutters/gemstones), commercial / picture stone quality, specimen for cutting/polishing, rough mineral specimen, and low-end parcels.
The miner gets to know the general grade type of opal he expects to find on his claim but hopes for surprises.
Everyone from miners to cutters have a grading system that enables them to sell.
At Opal Art Global our core products are, what we generally term, “scenic”. This product, necklaces, earrings & bolos (lariats), are cut from commercial/picture stone rough boulder opal.
Even though the rough opal has been graded into the above-mentioned parcel there is still a lot of diversity within.
Here is an example of how the 3 x 200L (44gal) drums of ‘picture stone grade’ rough on the back of the truck will be brought into the workshop.
If the rough is in the form of largish boulders (which it often is) we will use hammers to gently tap along the opal veins to break it down into easier handling sizes. Note if the opal veins are more gemmy in color we will go straight to the saw.
Sorting rough opal at workshop
First rough sort: cutters/rough – those pieces that will yield our core product type; obvious opal faces and interesting opal veins in the rock or “scenics.”
Second rough sort: mineral spec/souvenirs – to be cut (broken down/shaped) and polished.
Third rough sort: unusual individual pieces with mineral collectors in mind, and parcels of rough that will cut fun stones with lapidary enthusiasts in mind.
Once the rough has been sorted we address the first rough sort.
We go to the saw; we still may use a small hammer here.
Sorting semi-processed boulder opal
This sort is done once the boulder rock has been processed on the saw.
First sort: Product: When we cut the boulders, we slice off opal faces of color, chase veins and sort what we cannot use into absolute waste (rocks with not opal at all) and ‘trace.’
Second sort: Trace: is the term we use for pieces that have some opal in them but are not usable at that point in time.
Third Sort: Waste: We discard the absolute waste as clean fill.
The semi processed opal, from the first sort, that comes off the saw is then sorted into product type and finished.
Sorting the finished product – grading and pricing.
First sort: Product group: Once the opal has been finished (front and back) we sort into the product categories previously mentioned - Necklaces, earrings, unset stone, bolo’s etc.
Second sort: Drilling – small and large holes: we sort the pieces that need to be drilled into large/small hole size depending on whether they will be made into necklaces or earrings.
Third sort: Grading: Lastly, we sort/ grade according to color, size, presence of piece.
Light is very important when sorting boulder opal albeit it rough or polished.
When we ‘pick up’ opal from the mine we use the sun and when we get back to the workshop, we use both artificial and natural light.
Sunlight is the best light for looking at rough but a fluorescent light is best when scrutinizing the opal face for scratches.
When we sort the rough opal, we look at it wet and dry.
When the opal is dry you get a better idea on stability and cracking.
When the opal is wet there is a better chance to see thin hidden veins carrying color.
We prefer looking at a rough opal parcel for sale when it is dry.
Funnily the opal always looks better in the outback sun as opposed to when we get back to the coast, where our workshop is. 😊