New gal here! But not new to marble collecting. This was hard to photograph- under normal light this opaque mib appears solid black, but when I louped it, it came alive with flashes of aventurine in very unorganized bands covering about 80% of the surface. The collection it was hiding in was a majority of good but common machine made Alley's and Master's from the 50's or thereabouts.
Anyone know who made this? Measures right at 16mm plus a hair.