[Illustration: A
Topaz from stream gravels near Streeter, Mason County, Texas. Natural
size. Left to right: colorless worn pebble; emerald-cut pale-blue topaz,
weight 10 carats; pale-blue worn pebble, weight 205 carats; step out
sky-blue topaz, weight 13 carats; pale-blue worn pebble.]
[Illustration: B
Tourmaline crystals in schist from Llano County, Texas.]