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Betafo habit?
  
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Sante Celiberti




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PostPosted: Feb 19, 2021 06:49    Post subject: Betafo habit?  

Hello.

I occasionally come across the term "Betafo habit" regarding quartz.
I don't know if it's an official term or just plaing collectible, since I haven't find references in the basic literature.
Some years ago I bought this sample which shows a particularity: the alternating faces on the terminations have an extra X face topped by an elongated S face.
Is this the "Betafo habit"?
Any suggestions are welcome.

Best regards.
Sante



IMG_20210216_181159.jpg
 Mineral: Quartz
 Locality:
Betafo District, Vakinankaratra Region, Antananarivo Province, Madagascar
 Dimensions: 10 x 5 cm
 Description:
A very elengated S face on a barely visible (in the photo) X face.
 Viewed:  1687 Time(s)

IMG_20210216_181159.jpg



IMG_20210216_181413.jpg
 Mineral: Quartz
 Locality:
Betafo District, Vakinankaratra Region, Antananarivo Province, Madagascar
 Dimensions: 10 x 5 cm
 Description:
Another S face (opaque) under a normal Z face (lustrous).
 Viewed:  1684 Time(s)

IMG_20210216_181413.jpg



IMG_20210216_191445.jpg
 Mineral: Quartz
 Locality:
Betafo District, Vakinankaratra Region, Antananarivo Province, Madagascar
 Dimensions: 10 x 5 cm
 Description:
Detail of the first extra faces set.
An elongated X face topped by an elongated S face.
 Viewed:  1690 Time(s)

IMG_20210216_191445.jpg



IMG_20210216_191104.jpg
 Mineral: Quartz
 Locality:
Betafo District, Vakinankaratra Region, Antananarivo Province, Madagascar
 Dimensions: 10 x 5 cm
 Description:
Detail of the second extra faces set.
 Viewed:  1685 Time(s)

IMG_20210216_191104.jpg



IMG_20210216_191847.jpg
 Mineral: Quartz
 Locality:
Betafo District, Vakinankaratra Region, Antananarivo Province, Madagascar
 Dimensions: 10 x 5 cm
 Description:
Detail of the thirth extra faces set.
 Viewed:  1685 Time(s)

IMG_20210216_191847.jpg



IMG_20210216_192117.jpg
 Mineral: Quartz
 Locality:
Betafo District, Vakinankaratra Region, Antananarivo Province, Madagascar
 Dimensions: 10 x 5 cm
 Description:
The smaller crystals also show extra faces.
 Viewed:  1685 Time(s)

IMG_20210216_192117.jpg


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Amir Akhavan




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PostPosted: Feb 19, 2021 14:09    Post subject: Re: Betafo habit?  

There are no "official terms" when it comes to habits, just names for general appearences of crystals that people use or don't use, it's fairly wishy-washy, but there are some "well-established" terms. In the world of well-established terms, yours has a Dauphiné habit (single enlarged rhombohedral face).
A set of x and s faces on every other edge is what is depicted in all sorts of mineral text books as the most characteristic set of forms of quartz. So what you see on your crystal is what you will find at countless localities worldwide. Elongated s faces are common on Dauphiné habit crystals from the Corinto/Curvelo area in Brazil, for example, but basically, elongated s-faces are simply what you get when you put an s-face on a Dauphiné habit crystal.
I've never heard of "Betafo habits" but have seen s faces being referred to as "Betafo-type face" in the caption of a photo on Mindat (and the same specimen, in a photo from the very same dealer, shown as coming from the locality Itremo).

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Sante Celiberti




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PostPosted: Feb 19, 2021 16:42    Post subject: Re: Betafo habit?  

Thank you very much, Amir, for your reply.
It is a pleasure to receive information from one of the major quartz experts.

I knew that this quartz has the Dauphiné habit but, since none of my alpine Dauphinées show extra faces (but my alpine quartzes with classic prismatic habit do), I thought the combination of the Dauphiné habit with the alternating sets of XS faces and the frequence of this shape in the Betafo district had given rise, in the field of collecting, to the term "Betafo habit". Now I understand that the correct form can only be "Betafo-type face".
I must however observe that, to be so frequent these alternating sets of XS faces, I have not found any photos of them on Mindat even among the quartzes from Corinto, but only occasionally some X or S faces.
Of course, having the samples in hand would be different...

Thanks again and my sincere congratulations on your "Page".
Sante
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Amir Akhavan




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PostPosted: Feb 19, 2021 19:56    Post subject: Re: Betafo habit?  

Sorry for the misunderstanding, I wasn't thinking of "common x s combos" at Corinto/Curvelo, but common elongated s faces on Dauphiné habit crystals from there. "Common" is relative, of course, and with 55 mineral photos on Mindat's Corinto page it's not too likely to see them. And one has to put more effort in taking photos that show individual faces on crystals than most people are willing to do.
BTW, you can see x faces on some La Gardette crystals.
I hope I'm not getting across too harsh by saying there's nothing "correct" about "Betafo-type face". What would that even mean other than you see it often at Betafo? But you also see it often at Itremo, and at Herkimer, etc. etc.
It's just an s face :-)

Actually I'm just taking a photo of a Corinto Dauphiné habit crystal with an elongated s face to show an example of a crystal where the diagonal striation of the face *apparently* points to the r face.

As a compensation, I've attached a photo of an "all wrong" crystal from Gouveia, Minas Gerais.



rc_br_gouveia_Q701_1_15.jpg
 Mineral: quartz
 Locality:
Gouveia, Minas Gerais, Brazil
 Dimensions: 19 × 27 mm
 Description:
All wrong :-)
 Viewed:  1535 Time(s)

rc_br_gouveia_Q701_1_15.jpg



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Sante Celiberti




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PostPosted: Feb 20, 2021 15:06    Post subject: Re: Betafo habit?  

Hello, Amir.

I agree with what you say.
My first question was whether the term "Betafo habit" that I happened to came across (and certainly not just me) referred to a particular crystallographic form.
Having ascertained that it is a meaningless term, the only explanation of its origin is the whim of collecting world.
Thanks for your clarifications.

Sante

P.S.: Your "All wrong" quartz is really intriguing.
If you need some Tuscan quartz for your work don't hesitate to send me a PM.
Cordial greetings.
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Amir Akhavan




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PostPosted: Feb 20, 2021 17:03    Post subject: Re: Betafo habit?  

Just in case someone is missing it: the "all wrong" quartz is right-handed :-)
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