What type of crystal structure does rough spinal often exhibit?

Rough spinal typically exhibits a twinned crystal structure, which is characterized by the intergrowth of two or more crystal individuals. In the case of spinel, the twinning can occur in various forms, leading to the formation of distinct crystal shapes that still maintain a shared plane or orientation. This is significant in gemology because the presence of twinned crystals can lead to unique optical properties, and can influence how the stone is cut and polished.

Twinned structures in spinel can result from the conditions under which the crystals formed, such as pressure and temperature during their growth. Recognizing these twinned features is essential for gemologists when identifying and classifying spinel, as well as determining its value based on clarity and appearance.

While options like single crystals, aggregated crystals, and granular structures may apply to other minerals or types of crystal growth, they do not accurately describe the typical characteristics of rough spinel, emphasizing the distinct nature of twinned crystal formation in this gemstone.