Final answer:
Snowflakes are being described. They have unique and intricate shapes, and no two snowflakes are alike.
Step-by-step explanation:
The subject being described in the given lines is Snow. Snowflakes are known for their unique and intricate shapes, and no two snowflakes are alike.
Unlike sand, leaves, and pebbles, which generally have similar shapes and structures, snowflakes have a symmetrical pattern that makes them distinct from other natural objects.
For example, the passage mentions that the blanket of white observed near the Great Salt Lake was actually crystallized salt, which reflects the sun's rays. This description matches the characteristics of snowflakes, which also reflect sunlight and create a picturesque winter scene.