By "a fine-grained quartz" I mean a quartz made up of very fine quartz particles, like very fine sand. That's what I have and that's what you have, Linda. I don't know what would make a pure white quartz any harder to seam than others unless the epoxy isn't available in white. You say it's silver. I would ask your installer if they make a whiter adhesive.
Your seam mostly looks clean--not chippy. I can't tell how tight the seam is from a photo, but mine is a hair's width because they used an electronic seam setter to pull the slabs together. When you walk into my kitchen, the seam isn't noticeable. Whenever I see a photo of a seam on fine-grained quartz and it stands out like yours does, I feel it could be better.
Here is a photo of my Pentalquartz Botticino taken by a professional photographer using professional lighting.Is your seam this tight?
Q