What is chalcedony with curved or angular bands or layers that differ in color and transparency called?

Chalcedony with curved or angular bands or layers that differ in color and transparency is known as agate. Agate is a specific form of chalcedony, characterized by its distinct banding and layering. These bands can exhibit a range of different colors and may vary in transparency, leading to the striking appearance that is often sought after in jewelry and decorative objects. The formation of agate occurs due to the deposition of silica in concentric layers, resulting in the unique banded patterns.

While chalcedony itself encompasses a broader category of cryptocrystalline quartz, it is agate that specifically describes the layered variety with its colorful banding. Other options, such as jasper, refer to opaque varieties of chalcedony and do not display the same banding features as agate. Banded quartz typically isn't a term used in gemology to refer specifically to this type of chalcedony. Thus, the defining characteristics of agate, particularly its banded appearance, make it the correct answer in this context.