I have to thank my past self. I watche sand read a bunch of comments of people saying they always run out so I just collected all the ones I saw on the beach because I was a beach bob I am now level 63 and just crafted a assault rifle.
On Crystal Isles, at about 42 40 there is a little white lake. There is a waterfall in the lake, and on either sides close to the waterfall are around 1000 silica pearls, + the ones in the beaver dams. Just be careful because in my case there was a Yuty pretty close by.