Magnetite xls from Bolivia: Locality?

Another recent spate of specimens, this time from Bolivia...

The magnetites are clusters on a white to tan matrix, individual xls ranging in size from 25 mm to 1.5 cm. Octahedral, many intergrown stair-step fashion - many also at odd angles to one another. Shiny metallic luster - not dull - dark greyish-black (almost silvery) rather than deep black.

Anybody have any thoughts on where these might have come from? Possibly a recent find in the past year or so that are now on the market?

(There are WAY too many Bolivian localites in the database to wade through them all. Plus I expect there's probably a couple dozen sites that have magnetite listed for them.)

It's a cute little specimen: I'd hate to have to toss it out for lack of good locality info...

KOR!

Alan

It is great when family and friends put thought into purchasing mineral gifts for us collectors. It is just too bad that shops will buy and sell materials without good locality information. Non-collectors can't be expected to know that having the name of the country a mineral comes from is not enough to catalog a specimen with.

I know of a number of shops that absolutely refuse to buy materials for resale which are not adequately labeled. Alas, far too many other shops seem to be totally unconcerned - so long as what they put out sells...

Grumble, growl, snarl - and all that. :~}

Alan

The following location has a number of magnetites still coming from it (I have seen a number of dealers carrying the specimens). I was talking to a dealer this last summer and pieces are still coming out of there.

Cerro Luanaquino, near Machacamarca, Potosi, Bolivia

There are a mountain of these on the market at the moment, variously located as Oruro Bolivia, or Machacamarca Mine, Potosí Department, Bolivia, or Cerro Huañaquino, Potosí
Department, Bolivia.

The latter seems to be the correct locality, but undoubtedly Alfredo will be able to say for certain.

ian jones

Hello Everyone,

Yes, I have been to the locality a couple of times, and it amazes me how many dealers sell them with convoluted or obfuscated locality labels, then Collector who receives such a label enters it on Mindat, thinking he has a new locality! And I have to "patrol" the bolivian corridors, taking them back out again. (Haven't done it for a while; there are probably new ones in here.) Grumble, grumble.....

The magnetite crystals come from 4 small adits on Cerro (or "Mt." if you prefer) Huanaquino (with a ~ over the first n - can't do on my keyboard), which is roughly 20 km north of the city of Potosi. These are also sometimes labelled San Calixto or Calixto Prospect (name of one of the adit owners), or El Molino or Tarapaya (names of nearest villages, a couple hours hike away), "Molino Mine" (incorrect), "Machacamarca" (incorrect - a silver mining district 3 hours drive away), "Oruro" (incorrect - a city 6 hours drive away), "Pocona" (incorrect - a town 12 hours drive away), etc.

A friend of mine and I found the first magnetite crystals loose in sand in a gully around 1995 while prospecting for an apatite deposit. The magnetites are now worked by the local villagers exclusively for specimen sale; there is no iron mine here. The veins are narrow, really just coatings on fissures in the dacite rock. When starting a new adit, the first specimens are a bit oxidized, on weathered rock, then they get better and more lustrous as the rock gets harder; finally the rock gets so tough that they abandon the adit and start over again elsewhere nearby. I don't know the total number of specimens produced, but it is at least 2 or 3 tons, so far. The largest quantities were exported to the wholesale specimen dealers Topgem in Arizona, and Mikon in Germany. The highest quality specimens went, I think, to Brian Kosnar, a young dealer in Colorado.

Associated minerals are most commonly drusy crusts of feldspar (Anyone have an analysis or XRD?), and prismatic white hydroxylapatite. On a micro level, a large variety of Ti-rich minerals (Check the Mindat page for Huanaquino).

Cheers, Alfredo

Thanks, Guys!

I feared the answer would be: "There's dozens of mines producing such specimens - take your pick..."

Nice to know one can still track things down with the help of friends!

Season's greetings, and I hope you all have the best of holidays.

KOR!

Alan

Thank you Alfredo for the excellent explanation of the source of the Magnetite xls. Lloyd Brown

In anyone knows of a mineralogically similar occurence from other cuntries, I'd love to hear about it.

Merry Christmas to all,
Alfredo

Alfredo,

The only similar occurrence I know of is Laurel Hill, Secaucus, New Jersey, USA, but the specimens from there are far inferior. They are free-growing in fissures with chalcopyrite and other accessory species.

I was lucky enough to obtain a nice plate of these Bolivian magnetite crystals when they first came out. The specimen is a "sample" of the new material, obviously selected as an excfellent representation of the new material.

Chet

I believe alfredo helped me out too, with my magnetite from Bolivia. It is indeed from Cerro Huanaquino on a rhyolitic matrix(dacite), it is nice to hear from it again. Alan i have a picture in my gallery, if you want to caompare or so...

Cheers!
Philip