tom swift among the diamond makers

I am reading a book called the sackets it really good the book is a series with stories of the whole sackets this first one i am guessing is where the first sacket Barnabas sacket became rich his father had fought in wars and had tough Barnabas many things about swordsmanship so he was very good at handling the sword and they lived in a marsh or the fens as they called it. One day while he was working in a quarry he accidentally tripped and fell onto something hard. When Barnabas looked down he saw that it was a gold coin and the saw another but that was everything he could see so he slipped them into his pocket ad walked away knowing he would be being whatchjed.