It's kind of hard to do mineral identification from a photograph, but it looks like the mineral quartz to me. You can test this by trying to scratch it. If it's really hard (e.g. you can scratch glass with it) then I am probably right and it is quartz. However, if it is very soft (e.g. you can scratch it with your fingernail) then I am wrong, and maybe it is a softer white mineral (e.g. talc). But it mostly resembles quartz.