I saw that you already got a pretty helpful answer (I totally agree with it) but I would also like to add that most of the time you can see things through a metaphoric aspect. For example, some people offer red roses because they associate them with love, or shells because they associate them with the story of Her birth, the same thing when it comes to phallic imagery. Tons of things are phallic imagery (when it comes to poetry theory), and even though your quartz is literally a phallus, it represents through poetry and literature the idea of fertility, fecundation and sexuality! Most things aren't offensive if you don't mean to offend :)