These are rather interesting pieces - fulgurites, or specimens of "fused lightning" from North Africa, possibly the Sahara Desert.
When lightning strikes sand, such as on a beach or in the desert, the immense energy goes into the ground, fusing the sand along its path into sand-encrusted rudimentary glass, often as thin walled tubes. These are small examples and are mounted vertically on posts. You can clearly see that the two on the right are delicate hollow tubes. The one on the left is solid at the top but hollow at the base.
Left: gold coloured post, 3/8 inch (0.95 cm) wide, 1/4 inch (0.6 cm) deep and 1/2 inch (1.3 cm) tall.
Centre: silver coloured post, 3/8 inch (0.95 cm) wide, 3/8 inch (0.95 cm) deep, 1 inch (2.5 cm) tall.
Right: gold coloured post, 1/4 inch (0.6 cm) wide, 1/4 inch (0.6 cm) deep, 7/8 inch (2.2 cm) tall.