Classify the field, flag what is uncertain

Working sediment images always mixes clear calls with borderline ones. The decision here is not only naming a category; it is deciding, for each structure, whether the evidence is enough to call it confident, probable, or in need of a second review, and being able to say which two visible features drove that call.

Use the same test on every structure: is there a continuous, bounded matrix with broadly parallel sides and rounded or blunt ends, confirmed by focusing through the structure, before any cargo is read? A structure that fails this test is not a cast regardless of what it appears to contain, and it should be described as what it is (mucus, a fiber, a cell clump) rather than forced into a cast category. A synthetic fiber is the closer look-alike of the two non-cellular mimics: it can show straight, roughly parallel sides like a cast, but focusing through it shows a flat, uniformly thin strand with sharp, high-contrast edges at every plane rather than a solid, rounded three-dimensional matrix, and its ends are typically cut square, frayed, or tapered to a point instead of the smooth, blunt ends a molded matrix produces. That through-focus profile and end shape, not parallel sides alone, is the repeatable feature that separates a fiber from a true cast.

For structures that pass the matrix test, read the cargo next. Intact cells enclosed in the matrix make a cellular cast; granules of any size make a granular cast; lipid droplets or oval fat bodies make a fatty cast; a homogeneous, cracked-edge texture makes a waxy cast; and any of these in an unusually wide matrix is additionally described as broad. A structure that shows features of more than one category, such as a granular cast with a waxy segment, is reported with a mixed descriptor where the local procedure supports it, rather than assigned to a single category that does not fit the whole structure.

When a structure sits genuinely between two readings, for example a very faint hyaline candidate at the edge of visibility, or a granular cast where the granule size will not settle into fine or coarse, flag it for second review rather than guessing. Flagging is a legitimate outcome, not a failure to identify.

A confident call, a probable call, and a flagged-for-review call are all acceptable outcomes as long as the two features behind the call can be named.