  We study the Newton stratification in the $B_\mathrm{dR}^+$-Grassmannian for
$\mathrm{GL}_n$ associated to an arbitrary (possibly nonbasic) element of
$B(\mathrm{GL}_n)$. Our main result classifies all nonempty Newton strata in an
arbitrary minuscule Schubert cell. For a large class of elements in
$B(\mathrm{GL}_n)$, our classification is given by some explicit conditions in
terms of Newton polygons. For the proof, we proceed by induction on n using a
previous result of the author that classifies all extensions of two given
vector bundles on the Fargues-Fontaine curve.
