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The Square Tablets.

Last Updated: 31st May 2016

By Giuliano Bettini

Locality http://www.mindat.org/loc-252520.html
(Nibbiaia, Rosignano Marittimo, Livorno Province, Tuscany, Italy).

The mineral

On the hydrotemalites of this locality, many yellow-orange square tablets of an unidentified mineral were found.
Embedded into calcite veins.
Squares or rectangles, apparently tetragonal.
The calcite was etched away with cold dilute HCl.
Very bright, resinous, fragile.
Here are some samples.



Yellow orange square tablet. Other views. FoV: 1.5 mm.

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Yellow orange square tablet 2.

Yellow orange square tablet 2. Other views.
The last image is interesting. The crystal has a deep reentrant angle, thus showing two tablets.

FoV: 1.5 mm
FoV: 1.5 mm
FoV: 1.2 mm
FoV: 1.5 mm
FoV: 1.5 mm
FoV: 1.2 mm
FoV: 1.5 mm
FoV: 1.5 mm
FoV: 1.2 mm


Yellow orange square tablet 3.

Yellow orange square tablet 3. Other views. FoV: 1 mm.

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Yellow orange square tablet 4.

Yellow orange square tablet 4. Other views. FoV: 1.5 mm.

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Yellow orange square tablet 5. FoV: 1.5 mm.

Unfortunately this tiny crystal was broken during cleaning.
Only the yellow opaque lower part remained attached to the matrix. The top (the transparent yellow square) is blown away.

Yellow orange square tablet 6.

Yellow orange square tablet 6. Other views. FoV: 1.5 mm.
The last images show two tablets.

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Pic 3
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Analysis

What is this stuff here?
Obviously what comes to mind is: anatase.
However, as anatase, these tablets have characteristics quite different from those of anatase of this locality.
They have the following unusual characteristics (only one or more of):
- They are placed in a vertical position, not flat with respect to the matrix;
- The flat front surface is etched;
- The luster is resinous;
- They are very fragile;
- Are growing on a yellow orange amorphous mass;
- They are double tablets.

To solve the doubt, I have submitted a sample to the electron microprobe analysis.
The sample “Yellow orange square tablet 3”.
This tablet was chipped, cracked in the middle, so I sent half to John Attard, John Attard’s Minerals.
Here the results.



There is only Titanium and Oxygen.
Then we may conclude: anatase.

Thanks to Silvana Cosmi who provided many of the samples.




Article has been viewed at least 2344 times.

Comments

Interesting! Had you not had this analyzed I would have immediately guessed wulfenite. Perhaps brookite and rutile should be considered as well

Michael C. Michayluk
31st May 2016 1:21pm
I just noticed brookite from here looks quite different (as it should), but could some be rutile?


Michael C. Michayluk
31st May 2016 1:39pm
Hi Michael, in fact the hypothesis of Wulfenite was made, but was heavily contested lol.
http://www.mindat.org/forum.php?read,11,380993,381058#msg-381058

Rutile, "at sight" they seem anatase.
Many thanks for your comment,
Giuliano.

Giuliano Bettini
1st Jun 2016 1:27pm

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