parshat Tetzaveh: Identifying the Stones: יָשְׁפֵה - yāšəp̄ēh.

The last stone on the last row, that of Binyamin, is יָשְׁפֵה - yāšəp̄ēh. To cite JPS on Shemot 28:20:

כ וְהַטּוּר, הָרְבִיעִי--תַּרְשִׁישׁ וְשֹׁהַם, וְיָשְׁפֵה; מְשֻׁבָּצִים זָהָב יִהְיוּ, בְּמִלּוּאֹתָם.

20 and the fourth row a beryl, and an onyx, and a jasper; they shall be inclosed in gold in their settings.

yāšəp̄ēh certainly sounds like jasper. Indeed, according to the Wikipedia article on jasper:

The name means "spotted stone", and is derived from Anglo-French jaspre, from Old French jaspe, from Latin iaspidem, the accusative of iaspis, from Greek iaspis, via a Semitic language (cf. Hebrew yashepheh, Akkadian yashupu), ultimately from Persian yashp.

From the same article:

Jasper is an opaque, impure variety of quartz that is usually red, yellow or brown in color. This mineral breaks with a smooth surface, and is often used for ornamentation or as a gemstone.

And here is an image of a jasper:














Meanwhile, Midrash Rabba identifies יָשְׁפֵה, stating בנימין מרגליטוס - that Binyamin's stone was margalithos. Jastrow (pg 836) corrects the vav to a yud, and identifies it with Greek margarites chersaios, the name of a precious stone corresponding to יָשְׁפֵה.

I do not know to what this corresponds. margarites in general appears to correspond to pearl, but Jastrow avoids this identification. Anyway, here is a wikipedia article on pearls.

Jewish Encyclopedia did a much more comprehensive discussion of all these stones. See here.