Beth Owl’s daughter reminds me:

By the way, as I’ve been discussing on my website, this New Moon is also a second New Moon in one month, as rare as Blue Moons, but not as widely known (since by definition, they are invisible)! Folklore calls the second New Moon the Black Moon. It has also been called the Secret Moon,the Finder’s Moon, and the Spinner Moon. It carries with it all the deep, wonderful magic of the New Moon, like planting the seed, new beginnings, and sending out our intention in order to manifest our heart’s desires. Plus it is believed that the second dark moon is THE time of greatest power within the mysterious realms and any magick worked during this time is particularly powerful.