According to the literature, the Trujillo sediment was material transported from the northmost Texas panhandle and from the Triassic-age mountains of central and south Oklahoma.  Because of the prozimity of those mountains, the sediment is relatively immature, containing mica and feldspar along with significant rock fragments.  The mica is mostly restricted to the shales.

I took two small hematite cones, a fat one and a thin one to study the nature of the rock they formed in.  Small cones were chosen as they were much easier to cut into without access to good rock cutting equipment.  Because the analysis was done on only two samples it is not thorough enough to conclusively quantify the rock but does provide some indications of rock properties and variation as ot relates to the cones.  The two cones are pictured here.

In crossection, the two cones showed a characteristic difference usually seen between fat and thin cones, notably the degree of hematite cement.  These views show crossections in both indirect and direct reflected light.  As seen, thin cones have less hematite.  Crossections of larger thin cones usually show concentric three dimensional cones but I have no photos of these at present.

A close look at the tips of each cone hints at their properties. The sandstone of each is very immature with median grain sizes around the 0.5 through 1.2 mm. size.  Sorting is fairly poor, grains are subangular usually, sometimes subrounded.  See photos here.  Contrast between the two cone types are reflected in contrasts in the rock properties; sorting, roundness, and sediment maturity.  Thin cones have grains which are subangular to subrounded, moderately sorted, and quartz content of 40 to 70 percent.  Fat cones have subangular poorly sorted grains composed of 20 to 50 percent quartz.  See the cone tips here.

Within the fat cones The grain mineralogy can be seen.  This image shows the high percentage of pink potassium feldsapar found in fat cones.  There is so much feldspar, the rock sparkles in strong light, giving a false indication of mica.  The sparkle is cleavage surfaces of the feldspar grains, mica occurring mostly in the shales and much less abundant in the cone-bearing sandstones.

Within the thin cones there is much less evidence of feldspar.  This view of a thin cone interior shows the decreased feldspar presence,  lower hematite amounts, and lower matrix material in general.

This look at only two cones supports the assumption thin cones are formed in rock of better vertical permiability than the rock containing fat cones.  The better vertical permiability however looks to be a result of better sorting and cleaner, more mature lower matrix sandstone, rather than grain size.