MDAI forms thin flat blades with platinic chloride reagent. In aqueous solutions, the crystals are arranged as clusters of thin yellow blades with pointed tips. These blades appear bright yellow under crossed polars. The blades grow in loose clusters with longer blades in hydrochloric acid solutions. With platinic chloride reagent and MDAI dissolved in 10% acetic acid, the blades in the cluster are broader and larger.

The clusters hold together very well and can be readily studied by IR microspectroscopy. The spectral quality can be improved with careful selection of crystals and pushing multiple crystal forms together.