A while ago (4ish years) Jake Luciani implemented Lucandra (Cassandra as the store for Lucene indices) and Solandra (extension of Lucandra - solr on top of Cassandra). I used both of those at one point.
It was really interesting work.
OP - was elassandra influenced by either of those in anyway?
[1] https://github.com/tjake/Lucandra [2] https://github.com/tjake/Solandra