Bernardite : TlAs5S8

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Welcome to the mindat.org media viewer. Here is a quick guide to some of the options available to you. Different controls are available depending on the type of media being shown (photo, video, animation, 3d image)

Controls - all media types

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Other keyboard shortcuts:

1Fit image to screen
2Fill screen with image
5Display at full resolution
<Make background darker
>Make background lighter
spaceHide/dim titles and buttons


If the field of view (FOV) is specified for the photo, the scalebar appears in the left bottom corner of the viewer. The scalebar is draggable and resizeable. Drag the right edge to resize it. Double click will reset the scalebar to it's default size and position. If the scalebar is in default position, double click will make it circular.

Controls - Video

Video files have a standard set of video controls: - Reset to start, - Skip back, - Play, - Pause, - Skip forwards. Keyboard shortcuts: You can stop/start video play with the P key.

Controls - Animation (Spin Rotation)

Animation (usually 360 degree spin rotations) have their own controls: - enable spin mode. Note that while images are loading this option will not be available but will be automatically activated when the animation has loaded. Once active you can spin the image/change the animation by moving your mouse or finger on the image left/right or by pressing the [ or ] keys.

The button switches to move mode so that you can use your mouse/fingers to move the image around the screen as with other media types.

The button, or the P key will start playing the animation directly, you can interrupt this by using the mouse or finger on the image to regain manual movement control.

Controls - 3D Stereoscopic images

If a stereoscopic 3D image is opened in the viewer, the 3D button appears in the bottom right corner giving access to "3D settings" menu. The 3D images can be viewed in several ways:
- without any special equipment using cross-eyed or parallel-eyed method
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- on a suitable 3D TV or monitor (passive 3D system)

For details about 3D refer to: Mindat manuals: Mindat Media Viewer: 3D

To enable/disable 3D stereo display of a compatible stereo pair image press the 3 key. If the left/right images are reversed on your display (this often happens in full-screen mode) press the 4 key to reverse them.

Controls - photo comparison mode

If a photo with activated comparison mode is opened in the viewer, the button appears in the bottom right corner giving access to "Comparison mode settings" menu.

Several layouts are supported: slider and side by-side comparison with up to 6 photos shown synchronously on the screen. On each of the compared photos a view selector is placed, e.g.:  Longwave UV ▼. It shows the name of currently selected view and allows to select a view for each placeholder.

Summary of all keyboard shortcuts

1Fit image to screen
2Fill screen with image
3Switch to 3D display of stereo pair
4Switch left/right images in 3D mode
5Display at full resolution
<, >Make background darker/lighter
H or ?Show/hide this help page
PPlay/Pause Video or Animation
[, ]Backwards/forwards one frame (Animation only)
spaceHide/dim titles and buttons
up arrowShow information box
down arrowHide information box
left arrowPrevious child photo
right arrowNext child photo
shift + left arrowPrevious image on the page
shift + right arrowNext image on the page

Copyright © Philippe Roth
minID: 9XJ-2FT

Bernardite : TlAs5S8

Copyright © Philippe Roth  - This image is copyrighted. Unauthorized reproduction prohibited.
Largest Crystal Size: 50 μm

Bernardite crystals in parallel (and probably epitactic) alignment on a possible sartorite needle, lying directly on dolomite. The morphology of these macroscopically brown-red crystals is typical for Lengenbach bernardite. FGL specimen L-15-6729. EDX analysis (EDXPR_1088), photo & collection: Philippe Roth

Collected: 2015

This Photo was Mindat.org Photo of the Day - 18th Apr 2016

This photo has been shown 1152 times
Photo added:3rd Mar 2016
Dimensions:1280x1040px (1.33 megapixels)
Software:ACD Systems Digital Imaging

Other Views - click to switch

Discuss this Photo

PhotosBernardite - Lengenbach Quarry, Fäld, Binn Valley, Wallis, Switzerland

18th Apr 2016 08:07 UTCHerwig Pelckmans Expert

Dear all,

I was not familiar with bernardite, so I read its description on Mindat.

The mineral is said to be monoclinic, class 2/m.

The description of the photo mentions:

"The diagnostic hemimorphic morphology of bernardite is clearly visible"

I thought 2/m symmetry in theory excludes the possibility of hemimorphic crystals. Am I wrong, or is "something unusual" going on here?

Cheers, Herwig

MKA, Belgium

20th Apr 2016 15:44 UTCUwe Kolitsch Manager

You're right - space group P21/c doesn't allow hemimorphism - either these crystals are distorted or the ID is wrong.

Message sent.

20th Apr 2016 17:37 UTCPhilippe Roth (2) Expert

My designation is indeed sloppy and I shall change it (I wanted to point to the different terminations on both visible ends of the crystals). Yet, there is little doubt that this is indeed bernardite. The EDXS results (which I shall publish since doubts popped up), the morphology (inline with the crystal forms goniometrically measured by Graeser on a X-rayed crystal, Hoffmann et al., 1993, see below) and the paragenesis are all indicative of bernardite.

I just produced the attached drawing that roughly models the larger crystal on the left hand side of the SEM picture. The crystal forms used are those measured by Graeser, with the exception of {310} replaced by {210}.

PS. The next issue of Schweizer Strahler will contain a brief note on - among other things - a bernardite twin, a premiere.

20th Apr 2016 21:45 UTCPhilippe Roth (2) Expert

Two child documents have now been added (crystal drawing modelization and EDXS analysis). Thank you for removing the banishment of this photo.

21st Apr 2016 17:08 UTCUwe Kolitsch Manager

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