Wallangulla - Lightning Ridge Opal Mining History
Black Opal was first discovered at Wallangulla (Lightning Ridge) in the late 1880’s, possibly 1887, by a boundary rider named Jack Murray. The first shaft was sunk around 1901 to 1902 by Jack Murray, who lived on a nearby property. Shortly after the shaft was put down he was joined by six members of a shearing team on their way to a large property (Angledool) to the northwest. And this was the beginning of Lightning Ridge Opal Mining.
A little time after Murray sank the first shaft, Charles Nettleton , a miner from Bathurst arrived and commenced sinking shafts. And it was Nettleton who sold the first parcel of gems in 1903 for $30 which was less than a fiftieth of what he could have got five years later.
Lightning Ridge Opal Fields
The Three Mile — The most extensively worked and the most productive area in the region. And at one point in time there were 1,000 opal miners working this area. In recent years larger scale open cut mining is performed to extract opal.
Thurleys Six Mile — It is reported that the first shaft on this field was sunk in 1902. Sinking ranging from 6 m – 12 m. In some claims the Finch claystone was extremely rich in opal and included a lot of clear potch. The field was then abandoned for a long period of time until May 1970 when miners flooded in to the area and recovered many good quality black opals. And these quality opals were extracted in close proximity to where the first shaft on the field was sunk.
Nobbys (Old Nobby) — This is one of the first shafts to be put down on the Lightning Ridge opal field. At the foot of the ridge, Opal was initially found in gravel. A large amount of opal has been recovered from this area, however, the rocks are dusty, extremely hard, and difficult to work. Even the Finch claystone in this locality is a lot harder than on the rest of the field and the shafts here range from < 1 m to approximately 12 m in depth.
New Nobby (New Rush) — Intensive work commenced here in 1960 when a 12 m deep prospecting shaft returned precious opal. When word got out a rush to the area began, resulting in the sinking of around 100 shafts. Lenses of Finch claystone were found at depths between 5 m and 6 m and 10.5 m and 11 m.
Deep Four Mile — An area with an average sinking of about 18 m with no shallow ground. Good quality opal was extracted here back in the 1930’s from five claims. There are different levels of opal dirt present in the area and the deepest shaft is 28.5 m.
McDonalds Six Mile (The Six Mile) — Here the Finch claystone depth ranges between 9 m and 12 m on the crest of the hill and 1.8 m at the base. The best quality opals were found in the deeper ground.
Rouses Six Mile (The Six Mile) — This area is known to be near McDonalds Six Mile, however its location is uncertain. Rouses Six Mile was a rush on shallow ground and the sinking depths varied from 1.8 m to approximately 4.5 m. There was only two claims that produced any quantity of opal and much of that was in the form of large black “nobbies”.
Nine Mile — Shaft depths of around 12 m on the crest of the hill becoming shallower towards the base. The Finch claystone is red, caused by ironstaining, and the depth to the major Finch claystone lens is between 6 m and 8 .4 m below the crest of the hill. Potch was found scattered with the opal.
Shallow Belars — Workings range from 0.3 m to 3.6 m in depth. Some good quality opalized bivalves were recovered here along the contact between the overlying Wallangulla sandstone and the Finch claystone.
Hawks Nest — Sinking range between 1.2 m and 12 m. Lenses up to 2.7 m thick and in some shafts three opal bearing lenses intersected at 3.6 m, 6.9 m, and 12 m. Some good quality opal has been extracted from this area.
Bald Hill — The primary lens of Finch claystone occurs at depths of around 13 m with some areas producing five lenses. One 30 m deep shaft was reported to intersect eleven lenses AND each lens contained opal. Opal nodules frequently develop deep in the Finch claystone lenses which are usually over 4 m thick and contain beds of kaolinitic sandstone. Most of the precious opal that was recovered from this region was worked in an area only 120 m by 30 m.
New Chum and Old Chum — Opal lenses as shallow as 1.5 m were encountered in this area with most shafts ranging between 3 m and 10 m in depth. Some shafts had no intersections with the French claystone even though they were sunk to 15 m. On the side of the hill in the Old Chum location opal float was found in gravels and the diggings here were up to 3 m deep. Another point to note is a 100 carats stone was recovered from the New Chum area.
Grawin — 42 km southwest of Lightning Ridge is the opal field of Grawin. A large amount of opal has been won in this region particularly at Richards Hill and Hammonds Hill. Most opal in this location occur in seams with very few nobbies unearthed. Most gems won here are light in colour, predominantly green in colour, and are have a greasy lustre. Glengarry is similar to Grawin in many aspects. The opal here is always found in seams and there have been no recordings of nodules ever being won in this area. The opal-bearing claystone here forms at depths ranging between 2.7 m and 4.5 m and 7.5 m shafts were sunk over a distance of approximately 400 m.
New Coorcoran — A field first worked in late 1972 to early 1973. Varying depths from near surface to 15 m, depending on the position of the ridge. The most common precious opal colours won in this field are green or blue together with red.
Lightning Ridge Opal Mining Methods
Opal prospecting is done by working underground shafts, or by treating old piles surrounding shafts. Miners use their own initiatives and combinations of equipment to extract opal and their methods vary.
The traditional method to sink a shaft was to use a pick and shovel, with waste dirt being hauled up in buckets by hand windlass. While sinking the shaft the walls are checked for levels of precious opal or potch, then driven along the level usually with a pick . Opal dirt is then gently shaved away with hand tools until there is a visible sign of opal.
The simple methods of hand mining used to sink and drive shafts are now being replaced with much easier methods like jackhammers. Opal dirt is removed from the face to the shaft in buckets or wheel barrows and raised by windlass, or power and automatic self tipping hoists.
Hand mining methods are gradually being taken over by mechanical equipment. You can drill a 20 m deep hole with a 1 m diameter in a matter of hours with a Mobile Caldwell bucket drilling rig. A cylindrical bucket (kibble) about 2 m long and slightly less than 1 m in diameter can connect to the drill and be lowered to the bottom of the shaft to collect all the opal dirt dug out by the jackhammer(s). The kibble is then raised and the dirt it brought to the surface and dumped straight onto a truck. These drills are also used to dig air shafts, access shafts for miners and equipment, and hopefully, a never required escape route.
Blowers are used to suck opal dirt from underground and are located on the surface. These act like huge vacuum cleaners that extract opal dirt up through a pipe to load directly onto a truck. Bob Cats with a backhoe attachment break opal dirt and can be used to transport the dirt when a bucket is attached.
Open-cut workings using bulldozers are slowly progressing but restricted due to extremely high running costs.
Puddlers are used to treat opal dirt and operate like a large sieve. Pudders remove opal dirt from harder materials such as nobbies and sandstone. Many of the old dried out puddlers have been replaced by rumblers or trommels (revolving horizontal screens) which remove the smaller sized portions prior to wet puddling. Wet puddling is carried out by large concrete like mixers, called by agitators, that have mesh windows which allow the silt flow out.
Many of the stowed dumps of dirt from underground shafts of previous mining days have been reworked by puddlers to extract small opals. In earlier times small opal did not have much value.
T o see if any colour is visible in opal, pincers are used to snip Nobbies. If colour is showing a polishing machine will then be used to buff the opal to roughly identify its value.