Which crystalline structure is characterized by a thorny apple appearance?

The crystalline structure characterized by a thorny apple appearance is ammonium biurate. This unique appearance, often described as spicule or thorn-like projections, gives it a distinctive look under the microscope. Ammonium biurate crystals are typically yellow-brown in color and are associated with certain conditions, especially in the context of urinary tract abnormalities or certain metabolic disorders.

In contrast, struvite crystals appear typically as coffin-lid shaped crystals, calcium phosphate crystals often take on a more plate-like or amorphous structure, and cystine crystals can appear hexagonal but do not exhibit a thorny or spiky structure. Each of these other crystals has its own characteristic appearances and are associated with different medical conditions, but none match the thorny apple description attributed to ammonium biurate.