The Silk Road repeatedly opened and closed over the centuries depending on the vagaries of conquest along the route.
Given the enormous transport costs and risks, only the very highest value and lowest weight/bulk goods could be traded this way.
The route was lucrative, and fought over, wound up ruled by a succession of different conquerors who came and went, and all the time it was open, but the costs varied based on how many payoffs and to whom they had to be paid.
As a trade route, it was open for lapis lazuli, Indus Valley beadwork, obsidian, and a variety of other items going on back into prehistoric times. Chinese Silk wasn’t available until about 500 BC.