FMF - Friends of Minerals Forum, discussion and message board

[John S. White]

Okay, here is the moderator seeking help. At the Denver Show this past September I acquired some goethite in quartz from Brazil (see photo). The dealer had it labelled "cacoxenite" which is, of course, quite incorrect and he also gave the locality as Minas Gerais. Hyrsl and Niedermayr in their book Magic World: Inclusions in Quartz show a photo that looks very much like this and the locality is Rio Grande do Sul. Lieber, in his book Amethyst: Geschichte, Eigenschaften, Fundorte, shows a very similar photo but the locality is not provided. Gübelin and Koivula, in their book Photoatlas of Inclusions in Gemstones, Vol. 2, show a photo of similar-looking material identified as being from Minas Gerais. At the same time I have a very good friend who has been mining amethyst geodes in Rio Grande do Sul for many years and he has never seen anything like this specimen. The esteemed mineral dealer Luiz Menezes told me he has never seen anything like this from Minas Gerais, so there you have it. I was also very surprised to see that Mindat.org does not include a single photo of this material under goethite.

Does anyone out there know the precise locality, or at least the state in Brazil where this material comes from? I am confident that it is not found in both Rio Grande do Sul and Minas Gerais.

[Peter]

Dear John
I have in a collection of Brazilian minerals, I bought in 1970, a polished, tumbled specimen of the same labeled Cacoxenite! Will ask a very good friend about it. He has mined almost every deposit worth knowing in Brazil.
Peter

[Jordi Fabre]

John,

I checked it with few people in Brazil and they said that if the Quartz is a little bit yellowish (citrine) or amethyst it could be from Goiás. The Quartz have shadows or tints of yellow or amethyst?

[John S. White]

Oh please, don't introduce another state into the mix. I am 95% sure it is from Rio Grande do Sul, and am hoping for confirmation. Some of this material has a light amethyst tint.

[Luiz Menezes]

Hello Everybody:

It was a pleasure to accept John's and Jordi's invitation to join the Forum. I will try to cooperate as much as I can, in special on the matter I know better: Brazilian minerals.

About the goethite inclusions in pale amethyst, I have just told John that I had never seen goethite of this color and shape inside quartz from Minas Gerais, for me it looks closer to the goethite inclusions in amethyst found at Rio Grande do Sul.

I have just read now the opinion that it may have came from a locality in Goias state. Unfortunately I have not any experience with material from Goiás; it is a very big state, with plenty of ore deposits and different geological environments, including pegmatites, but I have not seen yet any goethite inside amethyst from there.

Regards

Luiz Menezes

[Jordi Fabre]

Welcome here Luiz. You are a great addition!

As soon as I get more infos from my correspondent in Goiás I will let you know.

Jordi

[Jordi Fabre]

[John S. White]

I can't wait!

[Jordi Fabre]

The promised examples of Goethites in Quartz from Goiás. Unfortunately both specimens are polished but I think that the similitude is notable.

[John S. White]

Jordi:

I must admit that this material does very much resemble what I have, but how do you know it is from Goias? It is really is from Goias, what is the exact locality and how about some photos of the crystals before being cut and polished.

[Jordi Fabre]

This is the definitive answer of my helpers in Brazil concerning the locality of these Goethite in Quartz:

Amethyst with goethite inclusions from Goias:

Merchants of rough and cut stones in Teófilo Otoni don't provide the actual location of the stones to avoid competitors on the field. Thus only give the name of the state (a huge state) and don't say the city where them appear

We will inform any REAL information we get about the right locality.