Yes… smithsonite is quite distinctive in form and color… your picture certainly matches this mineral ID.
smithsonite is zinc carbonate. Hemimorphite is another possiblity and is zinc silicate. A field test for carbonate can be used… if you can take a very small piece off the bottom side without ruining your specimen, test it with dilute hydrochloric acid… it will effervesce C02 bubbles. Alternatively you could put a drop of HCL on an inconspicuous spot on the bottom side… if it fizzes, it’s carbonate. Be prepared to immediately stop the reaction by spinkling baking soda on it and washing it thoroughly with running water. Use the bottom side to test for hardness by scratching it against softer minerals… Smithsonite is quite soft at 4.5…it also flourences faint pink or yellow with LW UV… the presence of copper turns it greenish blue and will damp down flourescence. SpG is heavy due to the zinc content. testing the whole specimen won’t work… it’s too big and has too many voids between the crystals to give an accurate reading. One thing that can throw you off is the presence of hemimorphite. Often found mixed with smithsonite… by appearance alone it does look like smithsonite with traces of copper to give it a green color… pure zinc carbonite is white. the last caveat is that it is difficult to identify anything from a picture alone.
did you get your specimen confrimed as smithsonite? you have something that is a beauty…