Pyrite Penetration Twin
Navajun, Spain
Size: 4.2x3.7x3.3cm, 2.6x2.4x2.3cm

Two crystals of the same mineral crystallize together in such a way that they are joined at a common symmetry or crystallographic plane forming a twinned crystal. When two parts of the twinned crystals grow into each other, they are called penetration twin.

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Aurelio Colomba said... June 7, 2014 at 4:49 PM

Thanks for all the things that always you share wirh the people arround the world. Thanks so much. Greetings from Argentina