You could easily read the necklace as a symbol of "wealth" itself – flashy, but false, in the end. Perhaps the revelation of the necklace's falseness at the end is meant to mirror the falseness of Mathilde's dream of wealth. Even deeper than wealth, the necklace might represent appearance, the world in which it's the outside that matters. Wealth belongs to the world of appearance, because money buys glamour. Mathilde's unhappy because of the way her own shabby house looks, and the way her lack of money prevents her from wowing the people she wants to wow with her natural charm and good looks. The necklace is glamorous, and it also gives her the opportunity to be the woman she wants to be, for one evening. Beneath the fancy exterior, though, the necklace is not worth anything – it's a fake. In that respect, it fits Mathilde's own situation at the party: though she fools everyone there, she's not really wealthy.
Tone:
Observant and Worldly-Wise, Detached but Understanding. Maupassant writes like a sophisticated fellow who knows the world, and particularly the world of "society" (high society). He's an excellent social observer who's willing to share his insights with his readers. Maupassant's descriptions of his characters are an interesting mix of detachment and intimate understanding. He sees into the emotions of Mathilde, his main character, clearly, and can make us as readers feel "inside" her world. But the narrator doesn't share her emotions, and we don't either. That doesn't mean Maupassant seems cold or indifferent to the characters, though. In the few telling moments when he moves beyond detachment, it is to express what looks like sympathy, or even admiration: Mme. Loisel learned the horrible life of the needy. She made the best of it, moreover, frankly, heroically. The frightful debt must be paid. She would pay it. Maupassant's detachment also keeps his narration from ever being judgmental, which is remarkable. You might want to judge