These gemstones are a durable quartz composite with the usual quartz hardness of 7. These stones begin as asbestos. A transformation begins when quartz becomes imbedded between the asbestos fibers. This process is somewhat like the petrification of wood. We have a lot more information about tiger eye and tiger eye like stones (Click Here)
These earrings are 16mm (.62") square and the wires are 3/4" long
These stones both look like the stone with the lines. We were unable to get the light to show the lines on both stones at the same time.