This cup is made of white stoneware with black speckles. The inside had been glazed with a food safe clear glaze and the lip with a food safe green.  Please note this cup does NOT have a thumb imprint or a shamrock but does have a fine, ribbed texture on the outside which is unglazed.
 
Dishwasher safe though hand washing is recommended
Please use a coaster as a precaution to protect fine furniture