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NZ's Barrytown polymetallic alluvial project gets a technical tick

Oldtimers tried to make money out of the alluvial gold at Barrytown in New Zealand, as did a series of big mining companies when they tried to mine associated ilmenite and zircon, but the key to success in the latest attempt could be the inclusion of another mineral they all overlooked, garnet.
NZ's Barrytown polymetallic alluvial project gets a technical tick NZ's Barrytown polymetallic alluvial project gets a technical tick NZ's Barrytown polymetallic alluvial project gets a technical tick NZ's Barrytown polymetallic alluvial project gets a technical tick NZ's Barrytown polymetallic alluvial project gets a technical tick

Tim Treadgold

Strong demand and limited supply have lifted the price of garnet, a hard semi-precious stone, which has developed a market as the preferred abrasive in high-pressure water-jet steel cutting.

For the Barrytown project, which yielded its first gold as far back as 1867, the addition of garnet to its mix of valuable heavy minerals means there is a fourth potential income stream which should be enough for it to reach the elusive goal of financial success.

The gold at Barrytown, which first lured prospectors to area 30km north of Greymouth on the west coast of New Zealand's South Island, was never in the same league as other goldfields in a country which housed some of the world's richest alluvial deposits.

Repeated attempts to mine gold on the coastal plain known as the Barrytown Flats yielded only modest results during a series of campaigns that ended in the 1940s when the last dredge was mothballed.

After the gold hunters came big-name titanium mineral and zircon hopefuls that included subsidiaries of Mount Isa Mines, Amax, North Broken Hill and Rio Tinto - but they all went home empty handed.

The new player on the flats which stretch for 17km close to the coast and up to 2km inland is Barrytown Resources, the major shareholder in the Barrytown Joint Venture which has a number of smaller shareholders including Aspermont Ltd, publisher of Mining Journal.

Low-key for the past few years, the plan for reviving the Barrytown project received an airing last week at the Australasian Exploration Geoscience Conference in a technical paper titled: "Old data, changed times, new resource?". Two consultants to the project, Luke Burlet and Graham Lee, explained how Barrytown had been upgraded from the status of largely forgotten alluvial gold and ilmenite prospect to a polymetallic project that is closer to development than ever thanks to the addition of garnet as a payable product.

The financial aspects of Barrytown were not covered in the technical talk which focussed on the way historical information had been reviewed and a range of omitted data from drill holes and gold assays included in the fresh assessment.

In effect, the return to Barrytown is a result of "mining" old and overlooked evidence to construct a new database supporting an initial resource of 69 million tonnes of material containing 8Mt of ilmenite (in the indicated and inferred categories), plus 12Mt of garnet, 220,000t of zircon and with gold as a valuable by-product.

Burlet and Lee said they had worked through documents dated between 1932 and 2001 held by the NZ Petroleum and Minerals department.

"A lot of the historical data for the project had been captured or partly captured by recent (circa 2013-14) work but a substantial amount of information, notably gold data, was only re-discovered during the 2018 resource modelling work," they said.

"This substantially added to the understanding of what exploration work for gold had actually been carried out and allowed for the modelling of gold.

"The outcome of trawling through the NZPAM reports was the compilation of a more complete, modern day, drilling database comprising ilmenite and gold sampling and assaying.

"The most important outcome of this process was the construction of a new "size fraction" table comprising logged sample intervals that record the mineralised sand information data such as dry weight, heavy mineral size fractions and contents."

Moving Barrytown from technical studies to a re-start on mining is now the challenge for the Barrytown JV with the likely mining method being a simple open-pit process dug to a depth of between 4m-and-8m to yield a low-cost concentrate.

Infrastructure and essential services in the Greymouth area are excellent and each of the products in the concentrate has a ready market with the key being the garnet which will be easily absorbed in the $US7 billion-a-year global abrasives market - a sector roughly twice the size of the ilmenite market.

Prices for all the proposed products from Barrytown are strong with garnet fetching around $US250/t.

While a relatively small heavy minerals project compared with other developments Barrytown does have the advantage of high ilmenite grades at 11.56% whereas most rival mines grade less than 5%, and lack the bonus of garnet and gold.

More work is required to turn Barrytown into a mine but with local land owners said to be in favour the major steps now are to finalise feasibility studies, secure government approvals and arrange funding for a project which could have quite attractive investment fundamentals - as well as being the final steps in a process started more than 150 years ago.