If I remember correctly, extruded powder is surface coated with burn deterrents in order the regulate its burn rates.
Rust, rubbing perhaps other things have removed this coating. It's obviously contaminated.
I've spent a little time researching deterrents and how they are applied. It appears liquid coating is the method, but how. Probably batch submersed then dried? Multiple times dipped or in different batch concentrations? Adherence integrity? Is deterrent coating what gives the powder that glossy appearance
EDIT......found it....
US3637444A - Process of making deterrent-coated and graphite-glazed smokeless powder - Google Patents
Text from an internet article:
Smokeless powder consists of
nitrocellulose (
single-base powders), frequently combined with up to 50 percent
nitroglycerin (
double-base powders), and sometimes nitroglycerin and nitroguanidine (
triple-base), corned into small spherical balls or
extruded into cylinders or flakes using solvents such as
ether. Other minor ingredients, such as stabilizers and ballistic modifiers, are also added. Double-base propellants are common in handgun and rifle ammunition. Triple-base propellants are more common in artillery guns.
The reason that they are smokeless is that the combustion products are mainly
gaseous, compared to around 55% solid products for black powder (
potassium carbonate,
potassium sulfate etc).
Smokeless powder burns only on the surfaces of the granules, flakes or cylinders - described as
granules for short. Larger granules burn more slowly, and the burn rate is further controlled by
flame-deterrent coatings which retard burning slightly. The intent is to regulate the burn rate so that a more or less constant pressure is exerted on the propelled projectile as long as it is in the barrel so as to obtain the highest velocity.
Cannon powder has the largest granules, up to thumb-sized cylinders with seven perforations (one central and the other six in a circle halfway to the outside of the cylinder's end faces). The perforations stabilize the burn rate because as the outside burns inward (thus shrinking the burning surface area) the inside is burning outward (thus increasing the burning surface area, but faster, so as to fill up the increasing volume of barrel presented by the departing projectile).
Fast-burning pistol powders are made by extruding shapes with more area such as flakes or by flattening the spherical granules. Drying is usually performed under a vacuum. The solvents are condensed and recycled. The granules are also coated with
graphite to prevent static electricity sparks from causing undesired ignitions.