Nancy, Tiny amounts of sand delivered in the original shot could
have created the spiral pattern you described. New Mexico is noted
for the ubiquity of dust in their environment! I lived there for 22
years. So I always ran my new shot, no matter who I got it from,
thru a couple of rinses. Then thru a couple of actual tumbling
cycles to burnish out any scratchs in the shot before I put the
shot to work. I, too, enjoy the more refined qualities of Dawn
dishwashing liquid. 
Chuck Hunner In southwest Florida where the
Whipporwills and Cardinals sing operas at dawn.