FMF - Friends of Minerals Forum, discussion and message board

[John S. White]

Here are two more of my single crystals that did not make the article in Min. Rec. I especially like the staurolite. Twinned staurolites are relatively common, but it is less commen to find an untwinned one of this size and complete all around. This one is 4 cm high. The locality is Fazenda Granials, Mines Gerais, Brazil.

The orthoclase is unusual in that it is perfectly transparent and colorless, and it has a very glassy luster. It is 2.5 cm high and is from South Betroka, Madagascar.

[Carles Millan]

Hi John!

As the section moderator, I'm very proud to have your nice specimens published here. I hope you will keep posting them and encourage you to do so. Please don't stop until you have nothing left.

Thanks,

[Jordi Fabre]

Absolutely!

Jordi

[Jason]

Hey John keep those crystals coming.. I read the min. rec. article and it's nice to see your letting us look mat some other fine examples of yours. I love the hematites nails.

[John S. White]

This is one of the rarest of the twins in my collection. It is about 2.3 cm and is, of course, from San Benito County, California, the famous benitoite locality. Neptunite often appears very black but the color in this photo is very close to the true color of this twin.

Photo by Pete Richards, sorry about the clay the twin is sitting on, I haven't time to photoshop it out.

[Ed Huskinson]

Wow John. Nice twin. To what do you attribute the weird brown colour?
I've never seen a benitoite like that... Hmmm. It is a different creature, that's for sure. What could possibly be the chromophore here?? Regardless, it fits right in with your "unusualities". Thanks for sharing.

Ed

[Jason]

Very cool...I have had lots of bens pass through my hands and have never seen any nep crystals that color. Like the nice symmetry of the twin too.

[Bluetriangles]

I saw the ? about why the neptunite twin appears red. Neptunite is a red mineral - very dark red. You can see ruby red flashes on most crystals when held in sun or bright light or when a crystal is small and thin it transmits red light when viewed. John's twin is heavily included with crossite which creates myriad small thin zones near the crystal surface hence the red is readily visible or in this case reddish brown since the crossite is typically greenish blue.

Neptunite is found in two twinning types from the Benitoite mine. His is a fairly common type found frequently where mineralizing fluids were able to bleed out into the wall rock during mineralization. The famous "Star of David" twinning (twinned on the c-axis) in benitoite only occurs in this region of the mine also. The rarest form of twinning in neptunite is that which twins on (001) miller indices. I have seen only 5 of these and am quite pleased to own 4 of them. Attached is a photo of one the 4.

[Jason]

Cool..thanks for the info BT. Well done

[John S. White]

Just back from a week in England where I acquired this little gem. It is, of course, a pyrite twin, but a type that I had never seen before. The so-called "iron cross" twin is well-known but that involves twinned pyritohedrons (also called pentagonal dodecahedrons), which when twinned with the twin axis being {111} cause crosses to appear on six different sides in an ideal example. I had never seen an interpenetration twin of cubes before, at least not in pyrite. This twin type is very common in fluorite however.

The unfortunate thing is that the dealer had no locality information for this piece. I am guessing that it is from Peru, but that will have to remain just a guess unless someone can cite another example that resembles this one. Even without locality information, however, I was very excited to find this twin. Sometimes little treasures like this turn up in the most unlikely places.

I am sorry for the poor photo, it is small (1.8 cm on edge) and I can't seem to get a sharp image with my poor camera.

[Gail]

I hear the weather wasn't too bad in England all this past week. I hope you had a marvelous time! Thanks for all these wonderful photos too John, really enjoyable.

[Jordi Fabre]

I can't be sure, but it looks to me as from Avarela, Portugal. We have some Portuguese member in FMF, hopefully they can help.

Jordi

[jorge santos garcia]

I can´t be shure too, but It does not seems to be from Avarela. The color of Avarela's pyrites seems more brassy. The cristals surfaces have paralel striations and sometimes curved edges and the interpenetration of cubes are more complex and usually make 90º angles.

The twins are usually smaller, loose cristals above 1cm are rare, but thats true they can reach bigger sizes.

Think it's strange that a Avarela's pyrite appears in a english shop, but in this global world, who knows.

So, I can´t say for shure it is or it is not from Avarela, it resembles a litlle bit, but I'm really in doubt.

Mindat have representative photos from Avarela's pyrites, it can help John.

Best regards

Jorge

[John S. White]

Thanks for the feedback but I think we can rule out Avarela. All of the ones I saw on mindat are pyritohedrons, not cubes. I would love to acquire one of those from Avarela, they are really fine.

Jorge, mine is very brassy also, my photo makes it look darker than it really is.

[jorge santos garcia]

Hello John

It would be a pleasure to send you a Avarela's pyrite. I know I have a spare piece somewhere, I will search for it. My mail is:

jsantosgarcia(at)gmail(point)com

Please send me your adress.

I know I have a problem with my cristalography knowledge, but wasn't aware it is so bad. No cubes at all at Avarela's pieces? oh boy!.

Regards

Jorge