Silicon Nitride vs Ruby bearing for Rega P5

it does prove a benefit. I used the ruby with a new subplatter and after adding the nitride there was a drop in the noise floor. steady as she goes and for short bucks it is a fair improvement. Is it worth it? Yes.

This is very interesting indeed. Let's analyze the facts regarding mass and hardness. Ruby/Sapphire has a density of 3.98G/CM3 whereas Silicon Nitride has a density of 3.44G/CM3, see a very close resemblence here?
On the MOHS scale (hardness) sapphire is 9, second only to diamond, whereas Silicon Nitride is 7.5, slightly softer in comparison. These 2 materials are so similar in density and hardness that IT is hard to believe anyone can discern a difference, especially given the small size bearing we are talking about here (3/16" dia).
I experimented with Silicon Nitride several years ago and since then I've been reading of massive claims of sonic benefit over a ruby or sapphire bearing. If you can hear a difference, brilliant, however I heard no difference at all. This is one of the overblown audiophile observations going, RE. bearings.

"When used to check certain soft materials like Aluminium, Cast Iron, ruby balls tend to accumulate small bits on their surface, rapidly leading to errors in measurements. When used in scanning applications, ruby balls are susceptible to wear, particularly on abrasive surfaces. Silicon Nitride Balls exhibits no tendency to accumulate material and better abrasive resistance. Scanning CMM users report up to 5 times longer tool life with Silicon Nitride Balls than ruby balls." Mr. Tom Breth, Q-Mark CMM Accessories.It seems that actual hardness is not the major issue here but the properties of the materials vis performance over time.