Jasper

Jasper closes the list of twelve breastplate stones in Exodus 28, assigned there to the tribe of Benjamin, the youngest of Jacob's sons, a placement medieval and modern commentators alike have sometimes read as fitting for the final position in the sequence. Jasper's wide natural color range, red, yellow, brown and green varieties all occur, made identifying "the" biblical jasper with a single modern variety a matter of some scholarly disagreement, since ancient naming conventions for stones did not map neatly onto the more precise mineralogical categories used today.

Modern gemology treats jasper as an opaque, fine-grained member of the chalcedony family, distinguished from clearer chalcedony varieties like carnelian and agate primarily by its density of mineral inclusions, which is what makes it opaque rather than translucent.

The name itself is one of the few in the list that can be traced with some confidence. The Hebrew yashepheh, the Greek iaspis of the Septuagint and the English jasper are the same word carried across three languages by borrowing rather than three independent coinages, which is unusual in a list where most of the names travelled less cleanly. What the word denoted is a separate question from where it came from, and several ancient uses of iaspis appear to describe a green translucent stone rather than the opaque material a modern catalogue files under the name.

The Exodus list is also not the only stone list in the Hebrew Bible. Ezekiel 28 names a set of precious stones that overlaps it, and the Hebrew and Greek texts of that passage do not carry the same number of stones as each other, which complicates any attempt to read one list against another as a check.

Jasper reappears in the Book of Revelation's vision of the New Jerusalem with a prominence none of the other eleven breastplate stones receives individually: the wall of the city is described as built of jasper, and the city itself, in the same vision, is said to shine "like a jasper stone, clear as crystal," language that reads oddly against jasper's ordinarily opaque character and has prompted centuries of commentary about whether the biblical author meant a stone modern readers would actually call jasper, or a different, more translucent gem known by that name in antiquity.

Whatever the precise identification, jasper's appearance at both ends of the biblical narrative, on the High Priest's breastplate in Exodus and on the walls of the heavenly city in Revelation, gives it a structural role in Christian scriptural imagery that most other named gemstones in the Bible do not share.

Jasper's placement in Revelation is more insistent than a single mention. It is the first of the twelve foundation stones of the city wall, and earlier in the same book the one seated on the throne is described as being in appearance like a jasper and a sardius, the two stones that close and open the Exodus breastplate list, which several commentators have read as a deliberate echo rather than as a coincidence of vocabulary.

The difficulty the passage creates for identification is the same one it creates for translation. If the stone in view is transparent, the word cannot mean what modern mineralogy means by jasper, and the usual scholarly resolution is that the Greek iaspis of the first century covered a range of chalcedony that included translucent material now filed under other names.