I've written about Dark Matter before - but I thought it was worth taking another look at it. Apparently - where it shines is not as a colour unto itself, but as a base for the high silver glasses.
This is a grouping of beads and the dark matter rods. This is the dark grey version - apparently there is a dark red version as well.
You can see a streakiness on the bead - it's very subtle and requires a lot of light to see it. When the bead is hot and goes into the kiln - it is actually quite interesting looking - purples.
This bead is a base of Dark Matter, rolled in silver foil, melted in, trails of ivory, encased Zephyr.
Experiment with this with the silver colours - see what happens!