The narrator describes Monsieur Lantin's first interest in the woman who would become his wife:
The young girl was a perfect type of the virtuous woman in whose hands every sensible young man dreams of one day entrusting his happiness. Her simple beauty had the charm of angelic modesty, and the imperceptible smile which constantly hovered about the lips seemed to be the reflection of a pure and lovely soul. Her praises resounded on every side.
This young woman's apparent virtue, her "angelic modesty," and one's sense that she has a "pure and lovely soul" are false or misleading. Her beauty and appearance of innocence are, in fact, symbolic of her deceitfulness. She is not virtuous—she later, we assume, has an extramarital affair with someone who sends her very expensive gifts and perhaps even money. Madame Lantin is not what she seems, either before or after her wedding. She is so charming and wonderful that her husband never assumes for a moment that she might be unfaithful to him. She is, in a sense, like her jewels: her apparent virtue is not real, and their apparent worthlessness is not, either. Both have symbolic and deceptive appearances.
In the short story "The Jewelry," also translated as "The False Gems," the symbolism can be found in the jewels that Madame Lantin owns, the importance she gives them, and the fact that they are evidence of her secret, double life. The jewels prove Madame Lantin is cheating. The fact that the gems are real is the big irony of it all because the jewelry symbolizes the fake nature of the Lantins' relationship.
Mrs. Lantin's jewels are, in the opinion of Monsieur Lantin, her husband, "just garbage." He foolishly thinks his wife's fascination with what he thinks are just glass and paste jewels is a mere caprice brought by the fact that they cannot afford real jewels. Still, Madame Lantin outdoes herself in wearing her diamonds and pearls to the theater, although each time she wears one of her typical, plainer dresses. Nevertheless, Monsieur Lantin loves his wife too much to care what her penchants may be.
After his wife's sudden death, Monsieur Lantin enters a period of grief that takes over most of his being. Not only is he extremely saddened, but his personal expenses, for some reason, seem impossible to cover. Since his wife managed the expenses, Lantin basically falls through the cracks and becomes impoverished.
To the last days of her life she had continued to make purchases, bringing home new gems almost every evening, and he turned them over some time before finally deciding to sell the heavy necklace, which she seemed to prefer, and which, he thought, ought to be worth about six or seven francs; for it was of very fine workmanship, though only imitation.
Once feeling the pain of hunger, Lantin resorts to selling one of the pieces of jewelry, assuming he would get very little money for it. He then finds out the jewels are real, and that a benefactor of his wife's sent gifts of this kind to her for a long time. Assuming that he is impoverished without his wife also leads to the realization that the benefactor may have also been giving Mrs. Lantin extra money.
Hence, the marriage that Monsieur Lantin missed so much was the real lie in his life, while those so-called fake jewels were real after all.