Chalcedony — quartz grown too fine to see the crystals — laid down in pale blue bands threaded with white lace. The most famous seam runs through a single farm in Namibia. The softness of the blue is the point: quieter than most agates.
When Mercury turns back, the hazard is in the mouth. Hold it at the throat, and re-read before you reply.
A deep royal-blue feldspathoid veined in white calcite, named plainly for the sodium in it. A Canadian seam near Bancroft supplied so much of it for a 1901 royal visit that it was briefly sold as Princess Blue.
A stone for the desk on a Mercury-retrograde day — for reading twice, and saying the true thing once.
This is today's sky for everyone. Tell (g)ode when you were born and it reads the sky against your chart.
Set up your chart