RPM
These marbles are named RPM because they give a sense of spinning at high speed (High RPM). Many RPMs have some aventurine in them. RPMs are almost always coated with clear glass, except the smallest ones.
This page last updated: 10 Nov 2005
"5/8 inch RPMs"
I make RPMs ranging in size from 5/8 to 1-3/4 inch. The price ranges from $20 for a 5/8" RPM up to around $70 or $80 for a 1-3/4 inch. Some other prices would be 1-3/8" about $40 to $50, 1-1/2" about $55
