Ronnie’s Road Trip: Mining the black opal

In another life with another wife, I once tendered on an irrigation job in Lightning Ridge, fell in love with the place, and vowed to the people I met that “I’ll be back!”

Back home and with relocating to ‘The Ridge’ high on my agenda, I told the wife of my wishes and was promptly advised that, “If you go there I will leave you!”

Well, marriage is all about compromise, they say … she got her wish and left me and I eventually got back to The Ridge, albeit 20 years late.

 

The Ridge

Lightning Ridge lies in a 270,000-square-kilometre geological feature called the Surat Basin (now known for its CSG operations) and forms part of the Great Artesian Basin.

The sediments of this basin, once a massive inland sea, are what hosted the formation of this precious opal.

Opal is found in horizontal sedimentary rock layers normally within 30m of the surface. This allows a relatively low-cost mining operation to start the rather dangerous extraction of this valuable gemstone.

For those who have yet to experience the opal mining fields, one of the first things you will notice about Lightning Ridge is that it appears to consist totally of broken-down machinery with a moonscape of earth piled up as far as the eye can see.

Delve deeper and talk to the locals and you will soon understand that this region of Australia, and the capital of the elusive black opal, is definitely no place for the weak, and that the mounds of earth and antiquated machinery are all part of the history of this great inland mining township.

Opal mining has been part of this town since the black opal was first found there in the late 1880s by a rabbit trapper named Jack Murray. However, its full commercial value was not recognised back then and it took till 1908 for the Grawin and Sheep Yard Opal Field to open up and increase the importance of the stone within the district.

The township was originally named Wallangalla in 1908 then renamed as Nettleton before the official naming took hold.

The name ‘Lightning Ridge’, so rumour goes, comes from an incident in which a shepherd, his dog and 600 sheep were struck and killed by lightning on a ridge in the area back in the 1870s.

As opal had been mined at White Cliffs since 1884, this area was considered the centre of the industry back then. In fact, the first opal mined at Lightning Ridge was taken by horseback to be sold in White Cliffs.

Today, most people would seriously have second thoughts about the air-conditioned drive, but 1000km return trip by horseback in those days … we are really kidding ourselves if we think we do it hard!

The innovators

Opal mining is definitely in a class of its own as the tyranny of distance forced the early pioneers to become innovative, creative and multi-skilled to mine the gemstone (not always with success).

The harsh conditions both above and below the surface also mean that you have to create friendships, mateship and loyalty far beyond what most people could ever anticipate. That feeling sits high once you meet the locals, most of whom have been here for many, many years and are proud to call The Ridge home.

To help the miners survive in this harsh climate and environment, the township has developed many supportive industries. There are fabrication shops, hydraulic and engineering shops, fuel, motor vehicle and trucking businesses, as well as a retail and service industry.

Out here, none are more important than the fabricators … these are the smarts and backbone of keeping the miners operational when things go awry, as they always do. These guys are the innovators, the forward thinkers, those who can take a miner’s roughly drawn sketch, add their tuppence worth and turn it into an engineering masterpiece.

These guys have not only had a huge input into making and maintaining the above-ground mining equipment but also into the development of the underground mining, extraction and fresh air equipment.

 

The luck of the draw

The mining tenements are all 50m x 50m square, so you have the luck of the draw when it comes to your plot.

To gain access to the underground, the miners drill a 1.2m shaft vertically to a predetermined depth. This depth is determined after the drilling of exploration holes and the assessment of the material for colour and value.

Opal can be found in as little as 6m or as much as 30m below the surface, which allows the smaller miners to still be competitive and viable should they make a successful strike.

Once the tenement is assessed and the access shaft and air ventilation shafts are drilled, the underground is opened for business.

Safely accessing the mine via the shaft has been a bone of contention for years. In some cases the shaft is accessed by steel or wire rope ladders but, in the mine we were fortunate enough to access,  an electric hoisting cage with safety barriers has been installed.

The air shaft not only supplies fresh air to the underground workers but also provides an immediate escape route should a cave-in occur or if a power failure closes down the hoisting gear.

All equipment is hoisted down the shaft, often in pieces for rebuilding underground if it’s too large for the hoisting cage.

Hydraulic and air lines are drilled to hangers on the shaft and extended in length as required.

Same but different

The main machine used underground is unique to the opal mining industry but is, in fact, a modification of a conventional surface earthmoving item … the most basic type of hydraulic backhoe arm!

Whereas the conventional backhoe arm has the support legs designed to hold the backhoe up off the ground, the underground version has the hydraulic legs redesigned to push vertically upwards so as to support the roof and wedge the digger into the floor.

The controls are the same as a backhoe but can be modified to suit the operator (although there are no final trim requirements down here)

The sedimentary seam is consistent and easily excavated by using the backhoe to dig from the face in a vertical top-to-bottom action and to a width of about 3m (but this may vary).

The bucket is seriously modified as there is need for high capacity; it is designed as a super-wide ripper with two or three tiger teeth attached to the cutting edge of a very small modified bucket.

The material falls, is scraped to the floor and dragged to the central backhoe pivot point below the operational controls where the fine materials are sucked to the surface via a 10-inch pipe.

In some other opal mines in the area the material is loaded with a small underground loader, deposited into a kibble-bucket and hoisted to the surface.

Either way, once the material hits the surface it is dropped into a hopper bin and fed into a trommel which spins the fine material from the coarse, making the final inspection of the opal bearing material more efficient and speedy.

Hydraulics, electricity and air are all delivered underground from a fixed designated truck-mounted base which enables easy movement between mining tenements.

Examining the opal-bearing material requires a keen eye and experience to distinguish between oxide (potch) material and opal-bearing material.

There has been many an unlucky miner who has lost sight of some significant gem-bearing material only for it to be found by a weekend fossicker armed with screen and shovel to find his ‘pot-a-gold’.

Back underground, as the diggings are opened up the issue about how and when to start propping the roof is always questioned.

Not unlike underground coal mines, black pine timber is used to prop the roofs, different to hard-rock mining’s use of rock bolts for roof supports.

Here in this opal mine, long, narrow tunnels are excavated, leaving the underground like a chequerboard with natural ground pillars left as props or roof supports for safety.

The issue here is that you may mine 5000 cubic metres of material in hope of finding 1kg of gemstone … which could be in the area you have left behind. Such is the elusive nature of the black opal.    

 

Death and change

Being out-of-sight, smaller and less governed and audited, these mining operations once had a “rip, tear and bust” attitude which resulted in many deaths and severe injuries.

However, legislative changes and a total clampdown on cowboy miners have now made underground mining a fully accountable and safe operation.

Inspections from the Department of Mineral Resources occur on a regular basis and the inspectors are extremely helpful in assisting the mining fraternity in every aspect of the mining operations.

 

Bust or boom

When the gemstone-bearing material is sorted, it is hauled to a washing plant made up of discarded and outdated concrete agitators that are recommissioned to wash the sand and clay off the gemstones to bring out the colours in the ore-bearing stone.

It is here that the experienced eye of the opal miner shines and he can quickly determine a good- or poor-quality stone in a flash.

The selected stones are then taken to the stone cutters, who carefully and painstakingly grind away in the hope of creating a valuable gemstone.

A good stone can be totally ruined by a poor or inattentive gemstone cutter, but on this occasion I was fortunate to witness an intricate, precise and delicate operation and to enjoy the thrill of the chase when the 60-million-year-old,  174-carat Dawn of Time pure Black Opal was polished and exposed to the public.

Many a man has paid the eternal price in the search; many have lost all of their possessions, family and soul in an effort to experience or even touch something like this … I was extremely fortunate to have borne witness to this amazing find and to follow its journey.

Ahh, The Ridge … you just gotta go there!