The Pentacle is the elemental weapon of Earth and the first of the four the Golden Dawn aspirant makes, at the Zelator grade. Its prescribed face is not a five-pointed star. It is a hexagram divided into segments and painted in the four colours of the elements as they sit within Earth, with the black and white ground of Malkuth behind them, so that the disc shows the element containing all the others rather than standing beside them.
Three confusions are worth clearing. It is not the pentagram: the five-pointed figure is a sign used in ritual, drawn in the air or on paper, and it is not what is painted on this disc. It is not the pentacle of the Key of Solomon, which uses the word in its older sense for the printed protective medals the book supplies by the dozen, each with its own inscription and purpose. And it is not the paten of the altar, although the two share a shape and a position.
What the implement is for follows from the element. Where the Wand acts and the Dagger divides, the Pentacle holds, and the discipline attached to it is patience with slow material things: money, body, ground, the parts of a working that cannot be hurried. It is made first in the grade sequence for that reason, and several commentators have noted that the order of the four implements is itself a teaching about where to begin.
Sources The Golden Dawn: The Original Account of the Teachings, Rites, and Ceremonies of the Hermetic Order of the Golden Dawn, 6th editionIsrael Regardie with Grimoires: A History of Magic BooksOwen Davies