This fine fluorite specimen is highlighted by the rare penetration twinning of a large crystal, measuring 2.2 cm across, right atop. All the crystals are lustrous and translucent to limpid and exhibit amber yellow cores along with purple zoning at the terminations. The specimen was mined in march 1994 and was in the Ross Lillie collection. RCL# 0713. Penetration twins from Illinois are quite uncommon! This one is a fine large display specimen overall, as well.