Anyone with some common sense would not pick a very large stone during gem gambling unless some green could be seen on the stone. Some gambling stone bosses would deliberately add some green colors on the stone just to get a good price for it. In fact, there was nothing valuable about stones like that. It was usually just a stone of very poor quality that consisted of a little bit of jade. They were usually also heavily flawed. As such, the big stones were usually unpopular when it came to gem gambling.
Unless they were ready to win the mare or lose the halter, no one would pick a huge rock.
The rock that Shen Qianshu picked was a water stone and not a mountain rock.
