FMF - Friends of Minerals Forum, discussion and message board

[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

[John S. White]

Jorge:

That is a very gracious offer and I will take you up on it. Many thanks. I was totally unaware of the pyrite twins from Avarela.

[Jim]

Great pieces, John

Please post more of your gem crystals, which happen to be my personal favorites. Of special interest is the twinned spinel from your MR article. Do you have an even better photo of that one?

Also, your morganite shown in the MR article is particularly charming. Congrats on the wonderful article.

Cheers,

[John S. White]

Two additions to my quartz collection, acquired at the recent Denver Show. The amethyst is from Artigas, Uruguay, and is 12 cm tall. The colorless quartz is from a relatively new locality that promises to produce lots of fine quartz groups, some of them quite large - Kullu Valley, Kullu district, Himachel Pradesh, India. Bert Ottens was recently there and he saw tons of specimens being removed. This piece has many different forms and is 6 cm across.

[Jim]

Nice scores, John!

By the way, I asked previously if you had better (or more) photos of your twinned spinel from the recent MR article about your collection. It would be great to see any posted.

Thanks,

Jim

[jimB]

I love the Artigas amethyst. A killer.