I know that this is really lignite, or black amber, but it seems like the etymology of this word must have been something like:
- Some mineralogist uses the term "jet" to refer to lignite.
- A second mineralogist, from The South, and having a very thick accent (those of you who have lived below the Mason-Dixon Line know what I am talking about) picked up the word and began to use it.
- Now, a third mineralogist comes along (who knew there were even this many mineralogists in the world?), this one being a Yankee. He hears the Southerner saying what he hears as "jay-et", which, if he were not so ignorant of his southerly brother's ways, he would know was equivalent to "jet".
- This third mineralogist then writes this word in some publication, yadda yadda yadda, the word "Jayet" is added to the dictionary
Let that be a lesson to you: Do not communicate vocally