That looks more like calcium deposits from dried urine to me. Guinea pig semen, or "boar glue" as it's often called, is very much just like that -- a gluey substance that dries hard onto stuff and is almost impossible to get off. I've had many a good piece of fleece ruined from hardened boar glue that wouldn't come off in the wash...
Some cloudiness to urine and some calcium deposits left behind from dried urine is quite normal for guinea pigs. However, if you ever start seeing very opaque, white puddles of urine in large quantities or piles of dried calcium deposit, you may want to consider reducing the amount of high-calcium veggies in your pig's diet. You can also monitor the texture of the calcium residue left behind by feeling to see if it's a soft, powdery substance or if it's gritty in texture. Supposedly, a grittier texture can indicate a potential buildup of sludge in the bladder, possibly leading to bladder stones.