Pectolite : NaCa2Si3O8(OH), Prehnite : Ca2Al2Si3O10(OH)2, Hancockite : (CaPb)(AlAlFe3+)O[Si2O7][SiO4](OH)
How to use the mindat.org media viewer
Click/touch this help panel to close it.
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
Zoom in and out of media using your mousewheel or with a two-finger 'resize' action on a touch device.
Use the mouse or your finger to drag the image or the view area of the image around the screen.
< and > at the left and right hand side of the screen move forwards and backwards for the other images associated with the media you selected. Usually this is used for previous/next photo in a gallery, in an article or in search results. Keyboard shortcuts: use shift + the left and right arrow keys.
< and > in the bottom center are used for switching between the photos of the same specimen. Keyboard shortcuts: use the left and right arrow keys.
> in the bottom center, raises the information box giving details and further options for the media, < at the top of this box then hides it. Keyboard shortcuts: use the up and down arrow keys.
? opens this help window. Keyboard shortcuts: use the H key or the ? key.
Other keyboard shortcuts:
| 1 | Fit image to screen |
| 2 | Fill screen with image |
| 5 | Display at full resolution |
| < | Make background darker |
| > | Make background lighter |
| space | Hide/dim titles and buttons |
Scalebar
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
- with stereoscope
- with anaglyph glasses.
- 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
| 1 | Fit image to screen |
| 2 | Fill screen with image |
| 3 | Switch to 3D display of stereo pair |
| 4 | Switch left/right images in 3D mode |
| 5 | Display at full resolution |
| <, > | Make background darker/lighter |
| H or ? | Show/hide this help page |
| P | Play/Pause Video or Animation |
| [, ] | Backwards/forwards one frame (Animation only) |
| space | Hide/dim titles and buttons |
| up arrow | Show information box |
| down arrow | Hide information box |
| left arrow | Previous child photo |
| right arrow | Next child photo |
| shift + left arrow | Previous image on the page |
| shift + right arrow | Next image on the page |
Update Dec 2022: This is another new parent photo using the Mindat interactive comparison tool with the same images as before. (To see both images, click on the TN.) The previous "vertical" comparison is now a child photo. Both versions use the same text.
May 2022: This is a new parent photo, posted to show the fluorescence. The previous parent image has been retained as a child photo, but I got rid of most of the old text because it was a muddle of information and misinformation.
The dealer’s label says “Pectolite Hancockite Roeblingite or calcite”. I was never able to see much in the way of fluorescence on this specimen with my wimpy old tube SW source, but a couple of Franklin experts were able to confirm the pectolite, as well as prehnite, with a “death star” caliber UV lamp – right in the brightly lit lobby of the Franklin Mineral Museum. (My thanks to Steve M. and Paul S.) But they said nothing about any Roeblingite.
Now that I have a new SW LED “flashlight” source, I can not only confirm, but also show , the pectolite (orange) and (minor) prehnite (violet-pink). I can also see why the dealer speculated that there might be roeblingite – there are patches of red fluorescence (mostly on another side but also a bit on the bottom of this photo). A sample of this material – still flourescing – was dunked in HCl, where it promptly fizzed away leaving a very small, platy, non-fluorescent, remnant. It is 95+% calcite – not roeblingite. (I may add a “caveat emptor” photo at some point.)
There is also an area of weak blue-gray fluorescence at the bottom. It is much brighter under MW and it actually covers a good deal of the specimen. Under a scope in consists mostly of crumbly white spherules. A small sample of this material dumped into HCl fizzed vigorously for about a minute or two, but then left behind an inert “core” (about 50% of the sample) that just sat there. Under the scope, this core appears to consist of clumps of tiny, poorly-formed, crystals. The experts I consulted did not remark on this stuff – probably because the SW response is quite weak – even in a dark room, never mind in a brightly lit lobby. At this time, I have no idea what it is. (Had it all fizzed away, I might have suspected “mineral F of Dunn”.) There are also some other unidentified minerals on the specimen, one of which is discussed under a child photo.
The hancockite listed on the dealer’s label can be seen in the upper left of the visible light image. There are additional thin layers of hancockite cross-cutting the specimen in several other places.
The UV image was made using a small SW UV LED “flashlight” positioned about 25 cm from the specimen. At that distance, the fluorescence of the pectolite is still naked eye visible, but it is not very impressive compared to willemite, calcite and etc, etc, from Franklin. To see it glow as in the photo, the source has to be < 5 cm from the specimen – and in a dark room. The 25 cm distance used for photography (in order to illuminate most of the specimen at once), meant that a 20 sec exposure using ISO 800 and F7.1 was needed for each frame.
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