Topotactical dehydration of chloritoid

The dehydration of the silicate mineral chloritoid in air and in vaeuo has been investigated by single-crystal X-ray methods and high-resolution electron microscopy. Vacuum dehydration yields an amorphous product, but the reaction in air produces a topotactical transformation to an anhydrous structure with an alteration in the stacking arrangement and symmetry. To be consistent with these observed facts, considerable modification to one component of the structure is necessary, a structural model being proposed for the anhydrous variant.