Where did Moses & the Isrealites get their gold?

Been gradually reading through the Bible and I have nearly finished Exodus. In it they are building various artefacts to aid their worship. They get instructions on how to build the tabernacle. I requires lots and lots of gold, as well as fine linens etc. What I couldnt work out is where they got it all from.
Assuming that they were a kind of slave race in Egypt (which brings another question to me) how would they have gold? Wouldnt their masters have taken any gold they had? If they did where did it come from? They couldnt even find food and water, hence getting it from rocks & manna.
This is a genuine queery and I am not after any foolish answers from atheists, please ignore the question and carry on your way.
Many thanks in advance for anyone who can help with this puzzle.