In Tennessee William's The Glass Menagerie, the glass unicorn is one-of-a-kind in Laura's collection.
When Jim and Laura meet again after so many years out of high school, they make a connection that they never made before: they talk and get to know each other. For years since Laura graduated, she has remembered Jim quite fondly. When she first discovers that he is coming for dinner, she refuses for quite some time to even answer the door with Jim and Tom arrive. Laura is terrified.
However, when Jim and Laura begin to speak, it is as if her dreams of Jim have suddenly come true. She has left the illusionary world her glass animals have provided her with and speaks to someone who tells her that she has value. Jim says:
You know what my strong advice to you is? Think of yourself as superior in some way!...Laura! Just look about you a little. What do you see? A world full of common people! All of 'em born and all of 'em going to die! Which of them has one-tenth of your good points!
Laura shows Jim her collection of glass:
Little articles of it, they're ornaments mostly!
Jim is hesitant to touch them, but Laura remarks that she trusts him. He places the unicorn in his hand...
...he's my favorite one...
Unicorns—aren't they extinct in the modern world?
Poor little fellow, he must feel sort of lonesome.
The unicorn represents Laura: she is one of a kind; alone in the world and fragile. Trustingly, she places her feelings in his hands.
As Jim and Laura continue to speak, they begin to dance to the music coming in through the open window. Laura has never danced before. Suddenly, as Jim leads her in a waltz, they bump the table and the unicorn falls; the horn is broken off.
Did something fall off it?...
...Is it broken?
Now it is just like all the other horses.
This foreshadows how Laura will be broken—as the unicorn as been. For a short time she feels special, but very quickly she finds herself feeling as if she is like everyone else—not at all special.
Jim talks on—saying Laura needs more confidence; he notes the things he likes about her: she has a sense of humor. He tells her that she is pretty, and that she's different, but "all the nicer because of the difference, too." He compliments her eyes and her hair—even her hands. Then Jim kisses her—Laura's first kiss. Laura is dazed. Jim is startled and self-deprecating, calling himself names. He admits:
I shouldn't have done that—that was way off the beam...I'm not in the situation to—do the right thing. I can't take down your number and say I'll phone...
No, Laura, I can't. As I was just explaining, I've—got strings on me, Laura, I've—been going steady.
In fact, Jim is going to marry in June. The unicorn is symbolic of the special time Laura spent with Jim, when she felt special—as she never has before. The broken unicorn is symbolic of the little piece of her that Jim has casually broken off because of his impulsive and thoughtless behavior. As if the unicorn might remind Laura of this experience—amazing and devastating—she gives the unicorn away to him, even though it was her oldest and favorite—like her cherished memories of him in high school. For now it is like all the other horses. With news of Jim's sweetheart, Laura no longer feels special. For a short time she was been alight like her animals, but now she is "shattered"—no longer shining.
First of all Laura reaction is casual. Taking into condsideration how much care Laura invest into caring for her glass collection, it seems odd when she is not upset that the unicorn lost its horn. On the contrary, Laura says that now he won't feel so different from the other horses. ("Now it's just like the other horses," ).The unicorn without the horn will fit in with the rest of the horses.
It is possible that Laura identifies with the unicorn. Laura has a problem with her leg which makes her feel like a outcast. She also lives in her own world, sort of speak, she daydreams and has problems making friends. In that sense, she is simlar to the unicorn - an unique fantasy creature. She may be seeing herself in an unicorn that has lost his horn thus becoming more alike to other horses and finding his place among them. Moreover, Laura who is paintfully shy may have hopes about fitting in as well. On the otherhand, Laura might not feel confident that she can have a rich social life but still be glad for the unicorn who has excaped his fate of being "different".
I think this is a metaphor T. Williams incorporated into the play. In addition, during that evening, Laura has been opening up to a guy that she had been in love with. As it turns out at the end of the evening, the man she loves is engaged to someone, but Laura still may be feeling better after an evening of conversation with someone. This could make her feel more hopeful and thus less likely to think negatively. So, it really is no wonder that she is not too worried when one of her precious figures is broken. Perhaps she is also trying to show that she is not as fragile as those glass figures and that she could blossom with a little help and understanding. Additional motivation for cool reaction could be more simple: she does not want to upset her brother. In any case, I would say that her reaction to the broken glass figure is an important part of the play.