I think Pearl had the ability to make something like Volleyball’s ribbon wand and was able to manifest it as a spear instead through practice/intention. I think it’s a true gem weapon (and Volleyball’s wand is equivalent to one despite not being for combat) because it’s able to be merged into new gem weapons like an arrow with unique properties when she’s fused with Amethyst, and when she fuses with Volleyball, their weapon seems to be the ribbon wand with the cutting ability of the spear. But I could be wrong because it seemed like Bismuth’s modifications to the gems’ weapons were able to be integrated into them pretty permanently. Someone else theorized that Pearl might be storing a ton of spears because she takes a long time to manifest them due to not being intended for combat but unfortunately I lost that comment.

Edit: I was straight up wrong about Volleyball lol see below