This question is just like saying "Is a book also a book." In other words, yes.
Birthstones are gemstones that are associated with a particular month and customarily worn by persons born during that month.
A birthstone is a jewel/gem that represents the month on which you were born.
A birthstone is a gem/jewel that represents the month on which you were born.
I'm born in June so I'm a pearl.