@change, check to see if you can depress them with the tip of a wooden toothpick. If so, then they should be plating bubbles. If not, then they are more likely trapped debris/dust as noted above.
"If you climb a good tree, you get a push."
-----Ghanaian proverb
"The danger we all now face is distinguishing between what is authentic and what is performed."
-----King Adz