Is the blob fish cartilaginous

No, the blobfish is in the group of fishes known as the bony fish (superclass Osteichthyes), in the class Actinopterygii, known as the ray fish. The other class in that superclass is the class of lobe fined fishes, Sarcopterygii. The cartilaginous fishes are in the class Chondrychthyes, which diverged from the bony fish over 500 million years ago, according to S. Blair Hedges in the online book The Timetree of Life (edited by S. Blair Hedges and Dudhir Kumar).