Hi All-

This thread seems to resonate with many!  I envy those still able to teach optics!

I may have missed a few replies so my apologies, but isn’t anyone 3D printing these?  When I first saw the question, I assumed there would be links to ellipsoids on thingiverse.com.  There are certainly lots of ellipsoids there to be had as starting points.

It seems to me that might be pedagogically useful to ask students to print their own for an assigned or self-selected mineral.  The equation of an ellipsoid is simple enough and playing with a 3D printer is motivating to many students.  You’d have to come up with some scaling standard, but then people could have a pile of indicatrices.  They could see how different the indicatrix is for orthoclase, muscovite, and sillimanite which is the advantage over the one-size-fits all versions that used to live in every teaching lab.  Or they create a series for variation in birefringence across a solid solution.  (And one shouldn’t ignore the uniaxial fun!)

Once you can print them you can let students cut them up to better visualize where the circular sections are located to cement their understanding that there are two optic axes.  You could challenge someone to print them with annotations on the surface to locate the points where the crystallographic axes exit the surface or to show the traces of any of the symmetry planes, etc.

Seems like a fun way to get students to noodle around and maybe think a little longer about optics.  At least that’s my two cents.

Cheers!
David Elbert

Hopkins Extreme Materials Institute
Johns Hopkins University
Baltimore, MD 21218
elbert@jhu.edu

From: Hummer, Daniel R via MSA-talk msa-talk@minlists.org
Date: Friday, January 26, 2024 at 1:52 PM
To: Peter Appel peter.appel@ifg.uni-kiel.de, Brock-Hon, Amy amy-brock-hon@utc.edu, MSA-talk@minlists.org msa-talk@minlists.org
Subject: [MSA-talk] Re: Biaxial indicatrix model
Hi everyone,

Around a year ago, I tried and failed to find indicatrix models for purchase, so I wound up constructing my own. It’s not the most time efficient way to go about it, but for anyone who enjoys DIY projects, it’s a fun exercise and you end up with a very robust teaching tool. You can do it by carefully cutting sheets of acrylic, polycarbonate, etc. (any soft but durable plastic) with a boxcutter, supergluing the pieces together, and then adding stickers to label the various axes.

Below is a photo of my biaxial indicatrix with all three elliptical sections and two circular sections. If anyone is interested in details, I’m happy to send printable templates.

Best,
Dan Hummer

From: Peter Appel via MSA-talk msa-talk@minlists.org
Sent: Thursday, January 25, 2024 4:38 AM
To: Brock-Hon, Amy amy-brock-hon@utc.edu
Cc: MSA public List serve msa-talk@minlists.org
Subject: [MSA-talk] Re: Biaxial indicatrix model

[EXTERNAL EMAIL ALERT]: Verify sender before opening links or attachments.
Hello,

not sure it this is what you are looking for. We use these simple wire models to illustrate the relationship between 2V, X, Y, Z axis and OA to the students. We have similar models for uniaxial positive and negative cases. I have no idea who made them but I like them and think they are helpful. (N.B.: On the left model part of the red circular section perpendicular to one OA is broken off, though.)

If you want, I can provide more fotos of them. In that case, just ask me directly.

Best, Peter

[cid:image001.jpg@01DA4F77.B9CD6840]

--
Dr. Peter Appel
Institut für Geowissenschaften, Univ. Kiel
24098 Kiel
Tel +49 (0)431 880 2900
Mobil +49 (0)151 15273436

Am 24.01.2024 um 17:01 schrieb Brock-Hon, Amy via MSA-talk <msa-talk@minlists.orgmailto:msa-talk@minlists.org>:

Hello! Does anyone have a template to build a paper model of the biaxial indicatrix? I have a TA who is interested in building one and I thought I would check here after googling.

Thanks for the help!
-a

Amy L. Brock-Hon Ph.D.
Robert Lake Wilson Professor of Geology
Associate Department Head
The University of Tennessee at Chattanooga
Dept. of Biology, Geology and Environmental Science
218-B Grote Hall,
615 McCallie Ave., Mail code 2653
Chattanooga, TN 37403
Ph. 423-425-4409

“Live as if you were to die tomorrow. Learn as if you were to live forever.”
~Mahatma Gandhi

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Hello Andrea and others

You may be interested in the following paper, which deals with visualisation of various types of anisotropy in minerals:

Healy, D., Timms, N. E., & Pearce, M. A. (2020). The variation and visualisation of elastic anisotropy in rock-forming minerals. Solid Earth, 11(2), 259-286.
https://se.copernicus.org/articles/11/259/2020/

The accompanying MATLAB toolbox ‘AnisoVIS’ for visualising mineral anisotropy, including visualisation of optical anisotropy/indicatrices is available on MathWorks https://www.mathworks.com/matlabcentral/fileexchange/73177-anisovis
and GitHub https://github.com/DaveHealy-github/AnisoVis

I think it is possible to download the 3D shapes from AnisoVIS for 3D printing purposes. If anyone manages to 3D print these objects in glorious technicolour, please let me know. As well as brilliant teaching/learning aids, I think they’d also make great gifts for mineralogists.

Regards,
Nick

A/Prof Nick Timms

Associate Professor | Deputy Director of the Space Science and Technology Centre | Deputy Director of Graduate Research | Honours (Earth and Planetary Science) Coordinator | Master of Research (Earth and Planetary Science) Coordinator
School of Earth and Planetary Sciences
Faculty of Science & Engineering

Read about our latest research: NASA returns asteroid sample to Earthhttps://theconversation.com/7-years-billions-of-kilometres-a-handful-of-dust-nasa-just-brought-back-the-largest-ever-asteroid-sample-214151

Curtin University
Tel | +61 8 9266 4372
Fax | +61 8 9266 3153
Mobile | +61 427 324199
Web | curtin.edu.au

[signature_4210887434]
Curtin University is a trademark of Curtin University of Technology.
CRICOS Provider Code 00301J (WA), 02637B (NSW)

From: Cameron Davidson via MSA-talk msa-talk@minlists.org
Date: Saturday, 27 January 2024 at 3:35 am
To: Brock-Hon, Amy amy-brock-hon@utc.edu
Cc: MSA public List serve msa-talk@minlists.org
Subject: [MSA-talk] Re: Biaxial indicatrix model
Fruits and vegetables are always a hit. I typically start with two kiwis (uniaxial +), and cut one perpendicular to the optic axis and one at an angle.  You can then use a piece of paper and some sharpies to outline the perimeters of your cuts and then draw in the resulting axes (helps to have some paper towels ready to quickly dry the paper before drawing). This works great since it reproduces what you do on the board when discussing various sections through indicatrices.

Large baking potato: If you use a caliper, it's easy measure the intermediate axis of the triaxial ellipsoid, then rotate the potato 90° (vertical axis rotation) and then rotate the calipers (horizontal axis) and mark on the potato where the caliper arms intersect the potato.  If you do this methodically in front of the students and walk them through what you are doing and why, they see it right away.  Now carefully cut the potato along the line you drew, stick it on a piece of paper, and wahla, you have a circular section.  Works every time.

Cam

On Wed, Jan 24, 2024 at 11:06 AM Brock-Hon, Amy via MSA-talk <msa-talk@minlists.orgmailto:msa-talk@minlists.org> wrote:
Hello! Does anyone have a template to build a paper model of the biaxial indicatrix? I have a TA who is interested in building one and I thought I would check here after googling.

Thanks for the help!
-a

Amy L. Brock-Hon Ph.D.
Robert Lake Wilson Professor of Geology
Associate Department Head
The University of Tennessee at Chattanooga
Dept. of Biology, Geology and Environmental Science
218-B Grote Hall,
615 McCallie Ave., Mail code 2653
Chattanooga, TN 37403
Ph. 423-425-4409

“Live as if you were to die tomorrow. Learn as if you were to live forever.”
~Mahatma Gandhi

MSA-talk mailing list -- msa-talk@minlists.orgmailto:msa-talk@minlists.org
To unsubscribe send an email to msa-talk-leave@minlists.orgmailto:msa-talk-leave@minlists.org

--
Cameron Davidson
Charles L. Denison Professor of Geology
Department of Geology, Carleton College
1 N College Street
Northfield, Minnesota  55057
507-222-4880

For a big room, a Spaghetti squash can be a fine uniaxial model.

Phil

On Jan 26, 2024, at 8:11 PM, Nick Timms via MSA-talk msa-talk@minlists.org wrote:

Hello Andrea and others

You may be interested in the following paper, which deals with visualisation of various types of anisotropy in minerals:

Healy, D., Timms, N. E., & Pearce, M. A. (2020). The variation and visualisation of elastic anisotropy in rock-forming minerals. Solid Earth, 11(2), 259-286.
https://se.copernicus.org/articles/11/259/2020/

The accompanying MATLAB toolbox ‘AnisoVIS’ for visualising mineral anisotropy, including visualisation of optical anisotropy/indicatrices is available on MathWorks https://www.mathworks.com/matlabcentral/fileexchange/73177-anisovis
and GitHub https://github.com/DaveHealy-github/AnisoVis

I think it is possible to download the 3D shapes from AnisoVIS for 3D printing purposes. If anyone manages to 3D print these objects in glorious technicolour, please let me know. As well as brilliant teaching/learning aids, I think they’d also make great gifts for mineralogists.

Regards,
Nick

A/Prof Nick Timms

Associate Professor | Deputy Director of the Space Science and Technology Centre | Deputy Director of Graduate Research | Honours (Earth and Planetary Science) Coordinator | Master of Research (Earth and Planetary Science) Coordinator
School of Earth and Planetary Sciences
Faculty of Science & Engineering

Read about our latest research: NASA returns asteroid sample to Earthhttps://theconversation.com/7-years-billions-of-kilometres-a-handful-of-dust-nasa-just-brought-back-the-largest-ever-asteroid-sample-214151

Curtin University
Tel | +61 8 9266 4372
Fax | +61 8 9266 3153
Mobile | +61 427 324199
Web | curtin.edu.auhttp://curtin.edu.au/

<image001.png>
Curtin University is a trademark of Curtin University of Technology.
CRICOS Provider Code 00301J (WA), 02637B (NSW)

From: Cameron Davidson via MSA-talk msa-talk@minlists.org
Date: Saturday, 27 January 2024 at 3:35 am
To: Brock-Hon, Amy amy-brock-hon@utc.edu
Cc: MSA public List serve msa-talk@minlists.org
Subject: [MSA-talk] Re: Biaxial indicatrix model
Fruits and vegetables are always a hit. I typically start with two kiwis (uniaxial +), and cut one perpendicular to the optic axis and one at an angle.  You can then use a piece of paper and some sharpies to outline the perimeters of your cuts and then draw in the resulting axes (helps to have some paper towels ready to quickly dry the paper before drawing). This works great since it reproduces what you do on the board when discussing various sections through indicatrices.

Large baking potato: If you use a caliper, it's easy measure the intermediate axis of the triaxial ellipsoid, then rotate the potato 90° (vertical axis rotation) and then rotate the calipers (horizontal axis) and mark on the potato where the caliper arms intersect the potato.  If you do this methodically in front of the students and walk them through what you are doing and why, they see it right away.  Now carefully cut the potato along the line you drew, stick it on a piece of paper, and wahla, you have a circular section.  Works every time.

Cam

On Wed, Jan 24, 2024 at 11:06 AM Brock-Hon, Amy via MSA-talk <msa-talk@minlists.orgmailto:msa-talk@minlists.org> wrote:
Hello! Does anyone have a template to build a paper model of the biaxial indicatrix? I have a TA who is interested in building one and I thought I would check here after googling.

Thanks for the help!
-a

Amy L. Brock-Hon Ph.D.
Robert Lake Wilson Professor of Geology
Associate Department Head
The University of Tennessee at Chattanooga
Dept. of Biology, Geology and Environmental Science
218-B Grote Hall,
615 McCallie Ave., Mail code 2653
Chattanooga, TN 37403
Ph. 423-425-4409

“Live as if you were to die tomorrow. Learn as if you were to live forever.”
~Mahatma Gandhi

MSA-talk mailing list -- msa-talk@minlists.orgmailto:msa-talk@minlists.org
To unsubscribe send an email to msa-talk-leave@minlists.orgmailto:msa-talk-leave@minlists.org

--
Cameron Davidson
Charles L. Denison Professor of Geology
Department of Geology, Carleton College
1 N College Street
Northfield, Minnesota  55057
507-222-4880

MSA-talk mailing list -- msa-talk@minlists.org
To unsubscribe send an email to msa-talk-leave@minlists.org