FMF - Friends of Minerals Forum, discussion and message board

[Robert Seitz]

I look forward to details of your story re setting up and using 3D printer for mineral bases.

[silvia]

The specimen contains a grouping of lustrous Galena crystals 6 cm on edge set on large lustrous black crystals of Sphalerite and accented nicely with sparkling colorless gemmy Quartz.

[Tobi]

Hi Silvia, again it's a pleasure to see your contribution here! As usual, you give further information, detailed description, an aerial photo of the locality, I really like that and I know I'm not the only one here ;-)

[silvia]

[silvia]

A fine large cabinet cluster of crystallized native copper without matrix. The specimen contains many Spinel twinned Copper crystals.

[silvia]

The Rocklands Copper Mine

I first became aware of this deposit way back in 2013, when a friend in the mining industry pointed out that a deposit consisting largely of Native Copper had been discovered near Mt Isa in Queensland, Australia. He had visited the mine twice in 2013, and had seen first-hand crystalline Copper nuggets exceeding 200 kilograms. He had also seen large aggregates of native Copper associated with sooty Tenorite. By large he meant 6 feet long or more. He had also seen specimens of crystallized Chalcocite associated with Calcite.

The only reason few specimens from the mine had been seen for sale is the mechanized nature of the mine and the no collecting policy of the original owners. A British company, UK mining ventures did a specimen recovery program in 2017, shortly before the mine was closed by the legal mandate of the Queensland Mines Department.

Had this mine been discovered in the 1800’s and worked by conventional mining methods of the day – hand picks and drives – specimens from the mine would be in the collections of some of the finest Museums in the world and in the collections of astute mineral collectors. I saw one spinel twinned Copper crystal from the mine 160 mm long by 30 mm wide.

The mine still has a lot of collector quality native Copper, Chalcocite and Chalcopyrite left, as the ore-body is so extensive in length and depth.

[silvia]

Rockland Copper Project

The Rockland copper project is located approximately 17km west of Cloncurry in north-west Queensland, Australia. Originally owned by CuDECO, the 1,600ha mine has been in receivership since 2020 with outstanding liabilities of over 60 million Australian dollars. Copper Resources Australia took over the troubled site in December 2020, more than two years after operations were suspended under former owner CuDeco, which went into liquidation in May 2020.

High grade copper ore consisting chiefly of Native Copper and Chalcocite were extracted from two mineralized bodies: Rocklands South and Las Minerale.

Las Minerale and Rocklands South - contain a unique supergene-enriched zone, characterised by pervasive high-grade Coarse Native Copper and associated Chalcocite ore, which persists from near-surface to depths of 180m, widths up to 45m. The combined native copper/supergene zone strike length exceeds 1200m.

Copper mineralogy at Rocklands is dominated by:

• Oxide zone (minor): Malachite, Azurite, Tenorite and Cuprite.
• Supergene enrichment zone (major): Chalcocite and Native Copper.
• Secondary sulphide enrichment zone (minor): Altered sulphides - Chalcocite and Bornite.
• Primary sulphide zone: Chalcopyrite (major) and Bornite (minor).

Mining methods included conventional open pit mining, an onsite beneficiation plant, a tailings storage facilities, waste rock facilities, surface water diversion, and site access.

Construction began in the first quarter of 2012 and open pit operations began in late 2012. The first concentrate was produced in July 2016 and was delivered to China Oceanwide International Investment in August 2016. The mine was officially opened in October 2016.

Geology

The mine lies within the Eastern Succession of the Proterozoic-aged Mt. Isa Inlier located in the Duck Creek Anticline. The mineralised lodes are hosted within a metamorphosed sedimentary complex with an east south east strike. The complex includes fine quartz and quartz magnetite sandstone, quartzite, siltstone, limestone and calcareous units, including scapolitic siltstone. Copper mineralisation is largely associated with intrusive medium grained dolerite that is prominent across the area and appears to be conformable with the sediments.

Copper mineralisation occurs in a sequence of partially parallel linear zones with a west-north-west trend. Twelve Cu/Co/Au ore bodies have been identified to date. The two most prominent mineralised bodies include Las Minerale and Rocklands South. Both the structures contain ore grade and thick copper mineralisation over strike lengths of hundreds of metres.

The mineralisation is associated with local alteration of biotite, actinolitic amphibole, red feldspar magnetite, calcite and silica. Substantial evidence of planar joints and fractures is available across the prospect area. The joints and fractures have served as dilatant channel paths to fluids that have metamorphosed and mineralised the rocks. The central part of Las Minerale hosts prominent polymict breccias.

[silvia]

ROCKLANDS MINE PROCESSING PLANT

The Rocklands Fixed Crushing Plant and Copper Concentrator were designed to treat 3 million tonnes of ore per year. The mill was designed to produce five saleable products:

• Coarse Native Copper concentrate
• Filtered fine Native Copper concentrate
• Filtered sulphide Copper concentrate
• Filtered Pyrite concentrate containing cobalt
• Filtered Magnetite concentrate

By late 2016, the operators had installed a copper casting plant. The casting plant produced half tonne copper ingots by melting coarse native Copper.

The key aspects of the treatment of the Rocklands ore were:

1. Recovery of the native Copper was divided into three products:

• Very Coarse (>40 mm – from crushing plant),
• Coarse (>1 mm by jigs) and
• Fine (<1>0.1 mm from spirals and tables),

2. The differential separation and recovery by flotation of the copper minerals and the pyrite containing cobalt,

3. Recovery of magnetite from flotation tailings.

The Plant installed at Rocklands utilized the following processes:

• A high-pressure grinding roll (HPGR)

• A rotary scrubber (de-agglomerator)

• Classifying screens

• Jigging circuit, consisting of Coarse, Intermediate and Fine jig circuits

• Spiral separation, consisting of rougher and scavenger spirals

• Table separation, consisting of rougher and cleaner tables

• Two belt filters, to filter fine native Copper product from spirals and tables

• Five thickeners (gravity, copper concentrate, pyrite (cobalt) concentrate, magnetite concentrate and tailings thickeners)

• Ball mill and cyclones

• Copper flotation, consisting of roughing, regrinding, cleaning, scavenging and re-cleaning

• Pyrite (cobalt) flotation, consisting of roughing, cleaning and re-cleaning

• Magnetic separation, consisting of roughing, regrinding, cleaning

[silvia]

A beautifully crystallized native copper specimen with no points of attachment.

[silvia]

Extremely large and lustrous sharp crystals of Tetrahedrite to 6 cm in size across the top of this crystallized Pyrite and Sphalerite matrix.

[silvia]

Enchanting specimen, comprising green velvety crystallized malachite in a large open pocket.

[Tobi]

[silvia]

[silvia]

Beautiful deep green botyroidal and crystallized malachite.

[Tobi]

[silvia]

[Tobi]

[silvia]

Classic Peruvian specimen! Hosts mirror bright golden sharp octahedral crystals of pyrite measuring to 8 cm in size.

[Tobi]

Spectacular and beautiful, Silvia!
22 x 18 x 8 cm of pyrite - what's the weight of it? ;-)

[silvia]