Question: I remember that every tribe has his own symbol, e.g. Benjamin's symbol is a wolf. What are the symbols of the 12 tribes?

(I am especially interested in knowing what the symbol is for Levi.)

Answer: 
Update on the stones of the hoshen / 12 Tribes, and their identification. This information is from my father's book "The Natural Bible: Judaism and the Environment", which will be published (be"h) by Berman House this spring. 

* *Odem*: clearly a red stone. Scholars suggest either red jasper, or carnelian sard (a type of quartz).
* *Piteda*: some sort of yellowish-green stone, probably topaz. Others suggest peridot, chrysolite or perhaps green-yellow chalcedony.
* *Bareqet* - translated in the Aramaic Targumim as *azmaragd*, a loanword from the Greek *smaragdos* for “emerald”. Some suggest beryl (of which emerald is a type). Others suggest the green malachite.
* *Nophekh* - its colour is unclear. Is it supposed to be sky blue? Some suggest turquoise. Or red, perhaps more likely (as suggested by the etymology of *nophekh*)? If so, it may be garnet.
* *Sappir* - a blue gem, but unlikely to be sapphire, even though the words are etymologically related. Most likely lapis lazuli.
* *Yahalom* - even though in modern Hebrew it means diamond, almost no scholars think this is correct. It appears to be a white/moon-like stone. Chalcedony is likely, and others suggest moonstone, amethyst or even jade.
* *Leshem* - apparently similar to *sappir*. Aventurine? Hyacinth? Turquoise?
* *Shevo* - almost everyone agrees that this is agate, perhaps striped or spotted.
* *Ahlama* - this is also fairly unanimous that this is amethyst, and the wine connection makes that even clearer (amethyst was associated in the ancient world with wine, and was reputed to prevent drunkenness).
* *Tarshish* - very unclear, especially since we don’t have a colour to associate it with. We don’t even know if it is the name of a stone or simply a precious gem that comes from the city of Tarshish. Scholars have suggested aquamarine, or some kind of beryl. The Targum suggests a stone associated with (the colour of) the ocean.
* *Shoham* - Most likely onyx, although the Targumim give *burla* or *birlewa*, which means beryl.
* *Yashfe* - again, one of the clearer identifications. Almost all scholars are in agreement that this is jasper. The Targum’s association with panthers suggests that it was spotted or veined jasper.
The [Targum Yonasan on Chapter 2 of BaMidbar](http://hebrewbooks.org/pdfpager.aspx?req=14084&pgnum=17) mentions the flags for each "super-tribe", i.e. cluster of three tribes that camped together:

* (2:3) Camp Judah's flag had stripes corresponding to the member tribes' stones [on the breastplate], namely red, green, and "shiny"; it bore the names of the three tribes Judah Issachar and Zebulon, with the inscription "Arise o G-d and may Your enemies scatter, and may Your foes flee from You", **with the image of a young lion** ...
* (3:10) Camp Reuben's flag had colored stripes corresponding to its member tribes' stones, namely *azmorar*, *shavziz*, and *savhalom* [the latter is probably diamond, I'll let you have fun with translating the others]; the names of its tribes, Reuben, Simeon, and Gad; and the inscription "Listen Israel G-d is our L-rd, G-d is One", **with the image of a young ram**; it should have been a bull [why?], but Moses switched it to avoid any reminder of guilt from the Golden Calf.
* (3:18) Camp Ehraim ... had stripes colored *kankirin*, *tarkin*, and *calf's eye*, with the names Ephraim Menasseh and Benjamin and the verse "And the cloud of G-d was above them all day as they traveled from the camp", **with the image of a child**
* (3:25) Camp Dan ... had stripes *sea-colored*, *birlevat chala*, and *apantor*, with the names Dan Naftali and Asher and the verse "Dwell Your Honor, G-d, among the tens-of-thousands and thousands of Israel" ... **with the image of a snake**.