Civil Code (Cap. 16), article 575

575. Nevertheless, if the thing united is much more precious than the principal thing, and has been made use of without the concurrence of the owner, such owner may elect either to appropriate the whole and pay to the owner of the principal thi ng the value thereof, or to demand the separation of the thing uni ted, even though such separation may cause injury to the other. When thing is considered as principal by reason of its value or bulk.