Corundum : Al2O3, Spinel : MgAl2O4, Magnesiohögbomite-2N3S : [(Mg,Fe2+,Zn)4(Al,Ti,Fe3+)10O19(OH)]2, Magnesiohögbomite-6N12S : Mg5Al11TiO23(OH)

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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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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:

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

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

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

minID: 877-5JM

Corundum : Al2O3, Spinel : MgAl2O4, Magnesiohögbomite-2N3S : [(Mg,Fe2+,Zn)4(Al,Ti,Fe3+)10O19(OH)]2, Magnesiohögbomite-6N12S : Mg5Al11TiO23(OH)

This image is copyrighted. Unauthorized reproduction prohibited.
Field of View: 8 cm

The sample is 4 cm x 4 cm.

In this sample the original Spinel is almost gone and has been replaced by olive-green coloured Corundum. Platy, hexagonal, black 5 mm Magnesiohogbomite-2N3S/6N12S crystals originally occurred on the face of the Spinel and were not altered in the conversion to Corundum. The sample was purchased from Dr. George Robinson in 1977.

JM, October 13, 2020, says that the two Magnesiohogbomite species are present in approximately equal amounts on these samples. They must be distinguished by analysis as there are no macroscopic features that are unique to only one of the phases.

This photo has been shown 799 times
Photo added:3rd Nov 2011
Dimensions:2272x1704px (3.87 megapixels)
Date/Time of Photo:30th Nov -0001 00:00:00
Camera:NIKON E4300
Exposure time:1/69s
Focal Length:8mm
Focal Length (35mm film equivalent):38mm
ISO speed:100

Other Views - click to switch

Discuss this Photo

PhotosCorundum - Lot 10, Concession 1, Bathurst Township, Lanark Co., Ontario, Canada

17th Jun 2012 18:04 UTCTim Jokela Jr

This is not corundum pseudomorph after spinel, it's just spinel (with a minute epitactic xls of hogbomite group.)

The corundum ps spinel crystals are quite distinctive, with weird pebbly surfaces, and a greyish color, nothing like the sharp, clean spinel, black to the naked eye, dark green with magnification, shown here.

I hope to soon have more info on this locality, and perhaps more on the hogbomite.

17th Jun 2012 18:45 UTCRob Woodside 🌟 Manager

message sent.

18th Jun 2012 15:28 UTCRichard Gunter Expert

Hi Tim:

The Corundum is here. The slightly greenish top to the Spinel crystal on the upper right side of the sample is Corundum. This is one of the few samples I have seen frm here that is in the process of transformation so the crystals are partially Spinel and partially Corundum pseudomorphs. I will post a child photo of a close-up on these compound crystals. I am glad to see you will have data on the Hogbomite as I have been curious where it fits in that group.

18th Jun 2012 15:52 UTCTim Jokela Jr

A closeup photo would be lovely, thank you!
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