Donate now to keep alive!Help|Log In|Register|
Home PageMindat NewsThe Mindat ManualHistory of MindatCopyright StatusManagement TeamContact UsAdvertise on Mindat
Donate to MindatSponsor a PageSponsored PagesTop Available PagesMindat AdvertisersAdvertise on Mindat
What is a mineral?The most common minerals on earthMineral PhotographyThe Elements and their MineralsGeological TimeMineral Evolution
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
StatisticsThe ElementsMember ListBooks & MagazinesMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day Gallery

Colorless cassiterite from Bolivia

Posted by Steve Stuart  
Steve Stuart February 20, 2012 04:28AM
Is there such a thing? I have a specimen out of a micromineral collection I acquired labeled as "colorless cassiterite, Potosi, Bolivia".

Also on the specimen are these off-white or tan needles. What might they be?


Steve Stuart
open | download - MM 772 Cassiterite 2a.JPG (75.8 KB)
open | download - MM 772 Unknown needles 1b.JPG (92.2 KB)
Alfredo Petrov February 20, 2012 04:35AM
Steve, yes, there certainly is such a thing as colourless cassiterite and, since pure SnO2 should be colourless, it's surprising that colourless cassiterite doesn't occur in nature more often. I suspect that your piece is from LLallagua, and that the needles are tourmaline.
Keith Compton February 20, 2012 07:50AM

Firstly all I can say is that I would love to acquire such a piece.
As Alfredo states it is surprising that more is not found. I suggest that the answer to that is that it is simply misidentified. It is not expected to be clear. May even be thought of by miners, at first glance, as valueless Quartz. Some of the recent Chinese material is very transparent - though I have not seen colourless - perhaps some will show up. It doesn't make it more valuable per se just very unusual.


Edited 1 time(s). Last edit at 02/20/2012 11:54AM by Keith Compton.
George Eric Stanley Curtis February 20, 2012 10:00AM
I live in Cornwall, with tin mines everywhere all around me, and cassiterite is fairly common.
I can confirm that colourless cassiterite does exist, though not as frequently found as the brown stuff.

All the best

United Kingdom, Cornwall
Steve Stuart February 21, 2012 03:50AM
Thanks for the responses. Just to be clear, my images have a 2 mm FOV, so these are micros! Llallagua sounds very plausible after reading the MR article in Vol. 37(2).

Noah Horwitz February 21, 2012 04:59AM
Does anyone know what usually makes cassiterite brown/black? Lead, iron, ...?
Alfredo Petrov February 21, 2012 05:14AM
Fe3+, I think. Hydrothermal vein cassiterite usually contains iron, sometimes a little indium too. Pegmatite cassiterite, on the other hand, often contains a little Nb+Ta.
Steve Stuart February 26, 2012 01:39AM
Here is another possible cassiterite on the same small micro-specimen. FOV is estimated at 1 mm; this is a crop of a 2 mm FOV image. Can anyone confirm visually that it is cassiterite?


open | download - Cassiterite 1c.JPG (361.7 KB)
Alfredo Petrov February 26, 2012 04:37AM
Looks tetragonal, so yes. I've often seen this shape before in black cassiterites, but not yet in a colorless one. (But then keep in mind that colorless cassiterite in general is far far less common than black ones.) Nice find.
Steve Stuart February 26, 2012 05:28AM
Yes, that was my impression. I did orient the crystal to look down the c-axis and the cross-section look square to me. I'll post the photos on Mindat.
Bart Cannon February 26, 2012 11:16AM
You are all going to suffer a colorless cassiterite story from me.

Back in the late 1950s a 25 pound pure lump of cassiterite was brought in to the U.S. Bureau of Mines Seattle Office.

It was found by a road grater operator near the Monroe, Washington city dump. The noise of the encounter was loud enough that the grator operator got out of his cab and pulled the specimen out of the road bed, and he delivered to the USBM where the late Elwin Magill identified it as cassiterite.

Since tin was a strategic metal at that time, he initiated a very detailed prospecting program to find its source. Careful and exhaustive stream sediment prospecting was conducted all up and down the nearby drainages. Nothing but a trace of tin in a roadcut near Skyomish was ever found.

The source of that boulder remained a mystery until around 1990 when Larry Jeffers, owner of a mineral shop in Seattle's Pioneer Square named Semantics Underground showed me a flat of cassiterites from Tin City, Alaska.

BINGO ! That was the stuff ! Light brown cassiterites grading to colorless exactly like the piece that Magill had saved on his dusty shelf.

The theory was that 60 years ago a miner returned to Monroe from Alaska had tossed out a lump of cassiterite into the Monroe city dump.

And thus another example of the scourge of field collectors was born. Specimen dumping hundreds of miles from their true source.

Just like back in 1965 when my little brother found an amazonite cluster on top of the dump of the Ibex Mine in Leadville, Colorado.

Pack dumping. It's a problem. But haven't we all done it?

p.s. I sell that colorless cassiterite as a electron probe reference material to this day. Better than synthetic tin oxide.

Sorry, only registered users may post in this forum.

Click here to login

Mineral and/or Locality is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © and the Hudson Institute of Mineralogy 1993-2018, except where stated. relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: January 17, 2018 22:11:24
Go to top of page