Thin plate of hard chert covered on both sides with a carpet of lustrous translucent red-brown sphalerite crystals of the variety known as "ruby jack" due to it's gemmy red color. From Joplin, Jasper County, Missouri. One side has two cubic galena crystals on the sphalerite. Excellent condition. Measures 4.5 x 4 x 1 inches ( 11.4 x 10.1 x 2.5 cm).