Final answer:
An opal triplet's arrangement includes a black backing at the bottom, a thin slice of natural opal in the middle for its color play, and a clear quartz or glass cap on top for protection.
Step-by-step explanation:
The arrangement of materials in an opal triplet from bottom to top is specifically designed to enhance durability and beauty. An opal triplet includes three layers. The bottom layer is typically made out of a black backing to provide support and increase the opal's color depth. The middle layer, which is the thinnest, consists of a thin slice of natural opal. This layer is what displays the opal's characteristic play-of-color. The topmost layer is made of a clear cap, usually constructed from quartz or glass, to protect the delicate opal below.
This structure not only protects the natural opal layer but also influences the way light interacts with the stone, creating the beautiful color displays similar to those seen in natural opal and other crystalline substances that exhibit an ordered arrangement of their internal components, as shown in various figures provided.