It's a small one, but not bad for the first ten minutes, thought Char, tucking the gemstone into her cleavage. Her Mining Guild uniform, as a necessity, was low cut, exposing a deep line in her bosom. As she put the stone between her breasts, the familiar tingling sensation flared up, then abated seconds later. She looked down, barely noticing a change. With a slightly disappointed sigh, she realized that was probably for the best, because she still had a long shift ahead of her. She continued to mine down a side corridor, about 60 meters below the entrance of the mine. It wasn't deep at all, but had never been explored before. In some of the deeper sections of the mine, miners needed to use two mine carts and a team of donkeys to pull them out. Char remembered in her first week with the guild a miner came out in a cart. Her breasts so big that the entire cart was filled and overflowing, with the miner's head barely visible underneath the mountains of flesh.
A useful bit of magic done by The Ancestors in the centuries past allowed for a very useful adaptation to develop among the women of Sein. Once a girl hit puberty and developed breasts, they could store objects within them. According to the legends The Ancestors developed this magic to aid in the hunter/gatherer lifestyle. Now though, it has proven to be very useful for the agricultural and mining industries. There are still tribes in the desert that fill their breasts with water to survive long treks, engorging them to the point where they can also be used as shade for the tribespeople as well.
Char was one of the younger miners in the Guild. She was only 23 years old, and was one of the two dozen new members accepted this cycle. Her natural breasts were just below average, roughly the size of a grapefruit, or perhaps slightly larger. She dreamed of being big. Not just bigger, but so big that she would draw the eyes of everyone, and make her name in the guild. Miners who returned from the depths with enormous breasts had their accomplishments painted upon the walls of the guild.
Over the next few hours of her shift, Char found a handful of other small gems, as well as some nuggets of iron, and a somewhat large moonstone, that she was unable to chip from the surrounding rock. By the time she had found the moonstone, her breasts has swelled from the grapefruit size she started with, to respectable watermelon sized mounds. They wouldn't win any prizes at a county fair, but they would get her some nods of respect as she crawled out of the mines. She sat and looked at the moonstone, unsure of exactly how big it was. She could chip it out, but that would risk damaging the product and result in a lower price paid for it by the Guild. She decided to make a generous guess as it it's dimensions and take some extra stone out with it. After an hour of lifting her arms over her now sweaty breasts, she was finally able to lift the moonstone free. It was easily the size of one of her breasts currently, and she giggled at the thought of how big it would make her.
She set it on the ground, and prepared to receive it. She undid one of the lines of leather cord on the front of her uniform, causing her breasts to drop and bounce into the loosened garment. The uniform was made of a fabric spun from a desert plant, that swelled when the rains came. This meant that the fabric could stretch as the miner's busts grew, but would still hold its shape and give some much needed support. The leather ties were enchanted, so that they could hold enormous weights without giving way.