Gallium- It has a melting temperature of about 85 degrees Fahrenheit, which is basically room temperature. If you hold this metal it will begin to melt in your hand.
Calcite with quartz from Huanggang Mine, Inner Mongolia, China. The pictured specimen is 7cm tall. The quartz at the center of the stacked calcite disks is better exposed in some of the specimens that they have at the show. Photo credit: Jeffrey A. S