British Association Report (1855), page 9:
“On the Existence of Acari in Mica”
bySir David Brewster
While examining with a microscope a thick plate of mica from Siberia, about 5 inches long and 3 inches wide, Sir David was surprised to observe the remains of minute animals, some the 70th of an inch, and others only the 150th of an inch in size. Some of these were enclosed in cavities, round which the films of mica were in optical contact. These acari were, of course, not fossil, but must have insinuated themselves through openings between the plates of mica, which afterwards closed over.