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Sunday, 28 September 2014

THE OTTERY MINE, TENT HILL NEAR EMMAVILLE NSW AUSTRALIA



The site in December 1967
The Ottery Mine is one of the few places in NSW where the public can go and get a good idea of what went on at a mine in “the good old days”. Usually, such sites are out of bounds, being on current mining leases or private land or considered too dangerous to allow people in. The Ottery is different – a lot of money has been spent to make the old mine site accessible and provide good information so you can see for yourself how it all came together.
The mine is close to the Tent Hill-Torrington road just a few km from the old tin mining town of Emmaville, itself about 40km from Glen Innes. For more information on how to get there and what there is to see, I recommend the following websites: Aussietowns – Emmaville (here), the Northern NSW site (here) and Aussie Sapphire’s Blog (here).
The site in May 1991
Before I move on to more technical stuff, here are few personal observations which might
enhance your


visit. I first saw this place in December 1967. The main features haven’t changed greatly since then – the chimney, the condensing chambers, the damaged environment (though this has been improved a lot by the mine site rehabilitation that has gone on since then.) In 1988 I collected specimens of pyrite and arsenopyrite there. You can still smell the sulphurous odour around the site. I observed (on the right near the car park) that there were a number of decaying wooden barrels which still contained a whitish substance. Maybe they are still there and perhaps it is refined arsenic oxide (as I first thought). More likely it is cement, which was delivered in barrels before the double paper bags of more recent years.
May 1991
On several occasions since then, I have been underground in the old workings (a potentially very dangerous thing to do), though most openings were blocked off even then. It was a real eye opener to catch a glimpse of the conditions in which the old time miners worked and to see the mineral veins in their natural condition in places in the rock walls.
As you will soon discover when you start reading about the Ottery, there were two main stages in the history of the mine. The tin stage began during the mining boom at Vegetable Creek (now called Emmaville) which commenced in 1872. Prospectors scoured the district, one of whom (Alexander Ottery) discovered the outcrop of the cassiterite-bearing veins sometime between 1875 and 1881. The mine was opened up in 1882 and the Glen Smelting Works was established to extract metallic tin. The site of the smelters is at the junction of the Emmaville-Deepwater and Torrington roads (Tent Hill).
From The Mineral Industry of NSW (EF Pittman 1901)
Eventually mining tin became unprofitable and the site passed into the hands of the firm William Cooper and Nephews (Australia), who then mined the arsenopyrite ore bodies to produce arsenic oxide which was widely used in the manufacture of sheep dip (1920’s on). This is the time when the surviving condensation chambers and chimney were constructed. There has been a lot of investigation of the site in more recent times and on several occasions when passing by on the way to Torrington I’ve observed drilling in progress on the hill. No doubt the price of tin is the key to any future mining there.
From The Tin-Mining Industry in NSW (JE Carne1911)
You could never call the geology of a site like this “simple”, but basically there are at least 5 quartz veins associated with fissures in a body of granite which intrudes claystone and tuff. This granite is probably related to the Mole granite to the north around Torrington. Arsenopyrite (FeAsS) and cassiterite (SnO₂) were the main ore minerals extracted, but pyrrhotite (Fes) and pyrite (FeS₂) are also present. As is common with such ore bodies, many other minerals have been identified in the ore, but are unlikely to be found as hand specimens.
To gain a better understanding of this place, and to see how it fitted in to the wider mining field, there are many good references you can download. Here are just a few.
A compendium of documents assembled by the Geological Survey of NSW may be found in DIGS (reference number R00045777). Doing a search in DIGS using the location “Tent Hill” and keyword “Ottery” will turn up much more. Of particular interest in the compendium is a document written by Harry Julius, whose father was the mine manager in the arsenic mining days.
The Minerama book title Cassiterite (1984) may be downloaded from here. See the part dealing with Emmaville in particular.
The Tin-Mining Industry in NSW 1911 by JE Carne (DIGS reference R00050677) was written near the end of the tin mining stage and has a good section on the Ottery Mine.
My You Tube gemstone playlist may be found here. I have three other playlists - the Blue Mountains, Glen Innes and New Zealand.
The Ottery Mine in 1922. From Grafton/Maclean mine data information

Sunday, 7 September 2014

WEBB’S SILVER MINE NEAR EMMAVILLE, NSW AUSTRALIA



Please take note: Practically all localities mentioned in these Blogs are on private property, under a mining lease or both. No-one should enter without permission from the landowner or lessee as appropriate.
The mine is marked "Silver" 7 (upper left)
I became aware of the existence of Webb’s Silver Mine (also known as Collison’s (NOT Collisions)) while I was still at school as a result of numerous visits to the late and much lamented Geological and Mining Museum in Sydney. This would have been in the mid 1950’s. The photos and specimens really piqued my interest in geology and mineralogy in particular.
It wasn’t until October 1988 that I made my one and only visit to the site when I rode my pushbike out there. The mine is reached by traveling 9-10 km after leaving The Gulf road, not far out of Emmaville, and then following a track to the right for a further 2.5 km. The mine site is usually described as being on Little Plant Creek, which runs into the Beardy River not far to the north. The map illustrated is the Grafton 1:250000 geological sheet.
My notes made that day mention a steel poppet head over a well-preserved shaft, numerous derelict sheds and ruins, 2X5 head stamper batteries, one in reasonable condition, piles of drill cores and specimens of galena, sphalerite and arsenopyrite on the dumps.
Photo by Wwoofa, Australian Lapidary Forum
Photo  by Wwoofa
Since then, several fossicking trips have be organised to Webb’s during the Emmaville Gemfest. The area is held under lease by Silver Mines Ltd; you can read their summary of the future prospects of the site here. I quote from this source: “Highest grade undeveloped silver project in Australia”, “a JORC compliant resource of over 12Moz of silver”, “From 1884 to1901 approximately 55,000t were mined at an average grade of at least 23oz/t”, “The current resources at a 70ppm Ag cut-off are approximately 1.49Mt @ 245ppm Ag, 0.27% Cu, 0.71% Pb and 1.56% Zn”.
The silver price is somewhat depressed at the moment (September 2014) which no doubt is quite depressing for the company, which is sitting on a great resource waiting for the right time to begin extracting it profitably.
Taken from Mole Tableland map DIGS R00041396
The classic reference to the geology of the Emmaville/Torrington area is TWE David’s “Geology of the Vegetable Creek Tin-Mining Field”, 1887. (DIGS reference R00031676, if you wish to download a copy.) The relevant pages are 156/9. David tells us that the vein was discovered by Mr L Webb, that it can be traced for several miles, that the metalliferous part of the vein is nowhere more than 3 feet wide and that the ore minerals present are galena, copper pyrites, mispickel and “a variety of grey copper containing silver and a trace of gold (silver fahlerz)”. We know copper pyrites as chalcopyrite, mispickel as arsenopyrite and fahlerz as “fahlore”, a complex mineral of the tennantite-tetrahedrite family, containing at least 5 metals (iron, copper, zinc, silver and antimony) as well as arsenic and sulfur.
Another reference, written around the time when mining was at its peak, is “The Mineral Resources of NSW” (DIGS reference R00051137) compiled by EF Pittman in 1901. If you want to read what mining was like at that time, start at page 111. The photo of the mine is taken from this source. This is definitely a book that readers of this Blog should download.
From Pittman circa 1901
The comprehensive reference “The Mineral Deposits of NSW (Markham and Basden, 1975, DIGS Reference R00037944) has a lot of information on the mine, commencing on page 379 in the section dealing with the Mole Granite. We learn that the main shaft is 203m deep, with 7 major levels, that 3 separate ore shoots were mined, the main one yielding over 40 000t of ore containing 760-920 g/t of silver as well as significant quantities of the other metals.
The various documents available from the Web which have been uploaded by Silver Mines Ltd will give you a summary of their prospecting and that of their predecessors, which has been quite extensive since mining was active. Here are several:
From DIGS: Review of Environmental Factors (Exploration Activities at Webb’s Silver Mine) 2012 (R00070524). This is a report prepared by Geolink Pty Ltd for Silver Mines Ltd.
Report for Silver Mines Ltd 2010. Here. This is a good summary of the geology and potential of the mineral deposit.
My You Tube Gem fossicking playlist may be found here. I have three other playlists - the Blue Mountains, Glen Innes and New Zealand.