I have become familiar with materials used to produce the AC 2, but not a Sapphire Tube armature.
I have found Ruby to be the least attractive as an armature when compared to a Cart' of same design with Beryllium as the armature.
Ruby and Sapphire are both Single Crystalline in their structure.
During a Demo's of very similar in design Cart's where different Styli were on the Cart's. The Group of attendees receiving the Demo's, found it hard to make the claim the Styli alone was the cause of the differences detected in the sonic.
It was more easily accepted that the Cart's Parts were most responsible for changes detected in the sonic, and the Armature and Damping Materials were material sensed to be items that has substantial contributing factors.