THE RUBY HILL GARNET DEPOSIT NEAR BINGARA, NEW ENGLAND NSW AUSTRALIA
 |
| Google Earth photo - the signpost coming from the north |
I’ve passed by this
place several times without going in. As there are many references to it as a
fossicking area, I suppose it must be open to the public, though whether this
is public or private land I’m unable to say. It is well signposted, more
visibly so when travelling south from Bingara, being on the right hand side of
the road linking Bingara to Barraba (commonly called the Fossickers Way).
The most precise distance from Bingara I’ve read is 18.6km, though from what
point in the town this was measured is not stated. There are no rubies there –
they proved to be garnets – but there have been several dubious claims of
diamonds being found there. More of this later.
The earliest
reference to the place appears to be DA Porter, “Notes on Some Minerals and Mineral Locations in the Northern Districts
of NSW”, published in the Journal of
the Royal Society of NSW in 1894. I read this many years ago and there
is no certainty that Porter is referring to the present day Ruby Hill. The next
reference is by JM Curran, in the same Journal in 1896. JF Lovering
quotes Curran as saying that a red, pyrope-rich garnet was found in a
coarsely-crystallising basic rock within the basalt at Ruby Hill. The easiest
reference to read from the early days is in “The Mineral Resources of NSW”, by EF Pittman, 1901. Search Trove.
 |
| Photo from Pittman, 1901 |
Pittman wrote as
follows: “A small hill, about eighty feet
in height, which is intersected by several basalt dykes, was pegged out some
years ago by a miner named Butt, who was attracted by some red crystals in the
basalt. Under the impression that these crystals were rubies, Butt drove a
tunnel, forty feet in length, in one of the hard basalt dykes, and only
desisted on being informed that the red stones were garnets and of no value.”
Pittman went on to tell of the search for diamonds on the same hill. He gives
the date 1889 for the formation of a diamond prospecting syndicate. The upshot of this was that “Ten diamonds, weighing in the aggregate four and one-eighth carats,
were obtained from it. The diamonds were remarkable in that they each had a
distinct depression or pitting on one of the faces.”
The first edition of “Gemstones”,
Mineral Industry series 18, page 66, (1960) (DIGS reference R00050829) throws doubt on the validity of
this discovery; however it also states that “in 1922 ER Dickens treated alluvial material in the vicinity of Ruby
Hill, and it is reported that some hundreds of small diamonds were obtained but
were not sold”. I wonder what became of them? There are other Ruby Hills in
NSW so perhaps these diamonds came from elsewhere. The second edition (1980,
DIGS reference R00050830) mentions only the earlier find.
 |
| Map from Pittman, 1901 |
What emerges from
these readings is that the garnets were found both in the breccia, which makes
up much of the hill, and in the dykes which intrude it. They are apparently derived
from fragments of eclogite found in the breccia (along with many other
types of rock, which is typical of brecciated volcanic pipes) and in the later
basalt, which they could have entered from the breccia when it was intruded by
the basaltic magma. They might also have been carried up from a considerable
depth from the same source rock as that penetrated by the breccia.
Lovering addressed the
nature of the eclogite fragments in an article in the Journal of the Royal Society of NSW in 1964 (Volume 97, pages
73-79). He stated “Eclogites occurring as
inclusions in igneous pipes are particularly important in that they may well
represent direct samples of the upper mantle caught up in the magma of the pipe
during its passage to the earth’s surface”. He prefers to call the
inclusions “garnet granulite” and adds that individual xenocrysts of garnet are
also found in the breccia and dykes, no doubt derived from the breakdown of the
granulite.
Because of the
(apparently) superficial resemblance of the occurrence to South African diamond
bearing kimberlite pipes, there has been quite a lot of interest in this
locality as a potential source of diamonds.
One such report, written by GL Rolfe for Anaconda Australia Inc. in 1979
(DIGS reference R00015604), concluded that the rocks there were unlikely to be diamantiferous.
Commenting on the garnets, the report states “The most common xenocryst in both the breccia and basalt is garnet. The
garnets are generally orange pink in colour, size varies
from 1 to 5mm. Reaction of the garnet with the magma during ascent to the
surface has resulted in kelyphitic rims one to two mm wide. The keliphytic rims
consist of clay mineral and zeolites. The rims are wider in the basalt than the
breccia, indicating a longer period of disequilibrium between the garnet and
magma”.
Reports
from fossickers of outings to Ruby Hill are few. Some say they found little or
nothing, others that there were numerous small garnets in the soil. Obviously,
the soil derived from the dykes is going to be the most productive, so these
places need to be identified from the map, rather than by digging at random. It
seems that nearly all the gems will be found in a small sized mesh sieve, a
coarser sieve being used to remove larger pieces of rock etc. There will
probably be no water on site, so dry sieving to concentrate the gems followed
by a dip in water you will need to take with you is the most likely approach.
There may be water in nearby Hall’s Creek, but this will almost certainly be on
private property.
Another useful reference: A thread from Prospecting
Australia’s website (here). There are some interesting photographs
in this thread, but as there is no mention of sapphire being found at Ruby
Hill in any other reference, the bluish stones may have come from
somewhere else. Some object for scale (such as a coin) in the photos would have
helped.
https://johnsbluemountainsblog.blogspot.com/2013/12/links-to-all-blog-entries-and-relevant.html All Blue Mountains blogs and videos
All New England and other Geology blogs and videos
Limestone Caves of NSW
Song Studies. Bible studies based on hymns and songs
Shoalhaven District Geology.
