I cannot tell what this insect I see is...?

I have a yard made of slabs of stone and every time I look at it closely, there are these tiny, microscopic-silverfish like insects that move very fast and jump like a flea when touched. I don't think it's tick because they don't look anything like it. There are thousands of this tiny, microscopic things and they start to move much after sunset. Can anybody tell me what this is?