FMF - Friends of Minerals Forum, discussion and message board

[vic rzonca]

Tessin habit dark smokey from Spruce Hill area of NH.

[Jason]

wrong topic for this thread scott, what about those Baryte and calcites you and bob found..got any pics of those?

[Scott LaBorde]

[Scott LaBorde]

I found these this weekend. I was pretty happy. Although they appear attached, they were actually only attached via the clay between them and are separate crystals.

[Jordi Fabre]

Good job Scott! ;-)

[Scott LaBorde]

Here are the two crystals in the previous post, after removing them from acid.

[Scott LaBorde]

I found two more this weekend.

[Pete Richards]

It's been about four months since the last post to this thread. In the meantime, i've had a chance to collect in North Carolina with Scott Laborde, though I did not find any crystals as spectacular as those he posted. He sent me home with one of his Tessin habit quartz crystals, and I finally got around to measuring it on the goniometer. The attached drawings capture the general habit, but not details/distortions due to the specific growth history

For those who can deal with Miller indices, the main faces that distinguish this habit from the typical prismatic habit belong to the steep rhombohedra {30-31} and {03-31}. An even steeper rhombohedron is present as a couple of faces.

Most interesting is the beveling face labeled 21-31. That is a label of convenience, and it correctly depicts these modifying faces as being basically parallel-edged between the two steep rhombohedra. The goniometric measurements only revealed {11-21} as a measurable face. These beveling faces are diagonally striated and are obviously an intimate combination of at least two forms, probably {51-61} in addition to {11-21}. In other terminology, these faces are an intermediate form between the s and x faces. However, these are not true faces, since they are composed entirely of little stripes of faces of different orientations.

Hopefully some will be interested in these geometric details of one example of the Tessin habit of quartz!

[Scott LaBorde]

I found this crystal this past Sunday in an alpine type fissure. The bottom of it looks as though it were either healing into a biterminated crystal or some kind of etching. To read the whole story behind it: https://www.rockhoundlounge.com/june13and20_2010.shtml
(link normalized by FMF)

Scott

[Scott LaBorde]

on the following website I did find a double terminated tessin crystal example:

https://www.faden.it/photo_gallery/curiosita_biterminati/053_croce_abitoalpino_formazza.JPG
(link normalized by FMF)

[James Catmur]

Those who would like help with Miller indices might find this tutorial from Cambridge university (which is also in Spanish) useful

https://www.doitpoms.ac.uk/tlplib/miller_indices/index.php

James

[Scott LaBorde]

In an attempt to resurrect this thread, I want to display a few fine examples demonstrating the peculiar "s" face's or combination of "s" and "x" faces that bevel the transition between two "m" (prism) faces on some tessin habit quartz crystals.

[Scott LaBorde]

A magnification of z31 above.

[Rizwan]

This is an interesting topic for me. As a learner, I just wanted to share a piece and would like to see if this counts as similar species..

[Scott LaBorde]

The tessin habit feature -- a narrowing of the hexagonal prism toward the ends (terminations) is certainly in your crystal. You could call it tessin habit although it is transitional (mixed) with normal habit as well. In other words there is not a smooth progression or narrowing toward the tip as found in my previous photographs. But it's all relative. A microscopic view of even the smoothest text book tessin habit crystal would show a less than perfect progression or narrowing. In fact all tessin's may be transitional in some sense, they just step or narrow inward in a much more regular and even interval

Please view Amir C. Akhavan's excellent website for what I consider the best online resource for quartz, "The Quartz Page".

Here he describes the various quartz habits:

https://www.quartzpage.de/crs_habits.html
(link normalized by FMF)