FMF - Friends of Minerals Forum, discussion and message board

[silvia]

Brief Discussion on the Barroca Grande Site

The Barroca Grande site includes the underground mine and portals, processing plant, mine offices and employee housing in addition to the active tailings disposal areas, and the Salgueira water treatment plant.

The underground jaw crusher situated below level 520 mRL in the mine delivers material no larger than 100mm in diameter (Run-of-Mine - ROM), to the Crushing, Washing and Screening (CWS) plant at a rate of about 160 ton per hour. After processing in the CWS plant, material greater than 0.8mm in diameter is fed to the Heavy Media Separation (HMS) plant. The material sent to the HMS plant accounts for approximately 80% of the original ore feed from the ROM.

Approximately 20 per cent of the original ore feed from the CWS plant is in the form of ‘fines’ and passes on to the sand and slimes shaking tables. Rejected material is either dumped as waste or sold as gravel.

Concentrate from the HMS plant is crushed in twin roll crushers. One of the roll crushers is dedicated to material 3 – 5 mm in diameter and this material is re-circulated to the HMS plant. Material less than 3 mm in diameter is hydrosized prior to concentration by gravity shaking tables. Gangue minerals, particularly quartz and other silicates are eliminated in this process. The sand tables’ concentrate, referred to as Pre-Concentrate, contains all the dense minerals, including Ferberite, Sulphides, Cassiterite and Siderite.

The pre-concentrate containing Ferberite, Sulphides, Cassiterite and Siderite are then screened into two fractions. The two fractions are passed over individual shaking tables. Sulphides are removed by flotation. The sulphides recovered then become feed for a copper circuit. The table concentrates, without sulphides, are dried and screened to prepare three sized fractions for dry high-intensity cross-belt magnetic separators. This produces a high grade Ferberite concentrate, and a non-magnetic cassiterite concentrate. The Cassiterite concentrate then goes to the Tin circuit for processing.

[silvia]

And Cassiterite too.

[Tobi]

Very informative, Silvia, thank you!

[James Catmur]

Obrigado

[silvia]

Beautiful green translucent lustrous crystals of Fluorapatite to 2 cm in size on a matrix of lustrous black crystallized Sphalerite with yellow crystals of Siderite to 2 cm. Chalcopyrite and Muscovite present, and perhaps minor Fluorite. The Fluorapatite crystals exhibit a bright orange fluorescence under UVA light.

[silvia]

[silvia]

[silvia]

Bright golden crystals of Marcasite to almost 2.0 cm in size stacked aesthetically on a matrix with Arsenopyrite, Calcite-Dolomite and crystallized Muscovite.

[silvia]

The specimen contains green tabular Fluorapatite crystals to 25 mm in size on a matrix of highly brilliant micro Muscovite crystals. A very pretty specimen!

The Fluorapatite crystals display bright orange fluorescence in the presence of UVA light.

[silvia]

MINE WASTE

The Barroca Grande Waste Dump lies directly above the Bodelhão Creek that flows south-easterly to the Rio Zêzere. Gravel, waste rock and sand tails are the main mine byproducts dumped at the site. Fine tails present the most challenging problems as they contain precipitate from Salgueira Water Treatment facility as well as the copper circuit tailings which contain up to 25% arsenic.

The old tailings TMF-1 area contains tailings deposited prior to 1985. The perimeter of this dam is approximately 750 metres for a total area of 35,000m2 area. The maximum depth is 50 metres at an elevation of about 600mRL. The mine operators are keen to re-process these tailings.

There are two other Fine Tailings Disposal Areas at the site designated TMF-2A which is now full, and a new disposal area designated as TMF-2B.

Fine tailings dam TMF-2A has been active since about 1998. At the end of 2013 it had a 1km perimeter for a total area of 69,000m2. Maximum depth was 50 metres at an elevation of 700mRL with a capacity of about 1,545,000m3. This is equivalent to about 3,347Kt of material. This dam, apart from sand and slimes, also received sludge from the water treatment plant, as well as the copper circuit tailings containing up to 25% of arsenic.

The fine tailings dam TMF-2B became active in 2019. It has a 1.6 kilometer perimeter for a total area of 135,000m2. It has a maximum depth of 70m with a maximum volume capacity of about 1,800,000m3.

[silvia]

The specimen contains black crystals of Cassiterite to 15 mm on a matrix with golden crystallized Pyrite, Arsenopyrite and Siderite

[silvia]

Panasqueira under the Microscope – Silvia’s collection

My partner organized a preliminary analysis of a sample of the suspected chlorite that coats many of the Quartz points of a specimen of Quartz with Arsenopyrite that I uploaded to my collections page.

Preliminary analysis indicates that the green spherical crystals that coat many of the Quartz points on the specimen in our collection are Clinochlore. Three samples were sent for analysis, and the sample used in the analysis is shown in the photo of the XRD.

We have asked for a complete elemental analysis to be conducted on the remaining crystals, and I will post the results when available.

[Sante Celiberti]

Hello, Mrs. Silvia.

Yes, almost certainly Chlorite Group.
I have a similar specimen somewhere labeled as Chlorite Group.
As you know, Clinochlore also is mentioned in Panasqueira.

I appreciate this opportunity to compliment your magnificent locality collection.
My best regards.
Sante

[silvia]

[silvia]

A cluster of Siderite crystals the prominent crystal being 5 cm wide. This is set in a cluster with crystallized Ferberite and Arsenopyrite, pale purple translucent crystals of Fluorite to 5 mm on edge across the front of the main Siderite crystal cluster.