Boron Cantilever and Ruby Cantilever, Why Ruby?

With respect to Be, its the oxide(s) that are toxic. For years and years the electronics industry commonly used BeCu (Be copper) alloys in connector pins and relay contacts. But, as with lead (solder), our big brother EPA and other regulatory agencies have decided to ban its use for "our own protection".

Boron is a very common environmental element, and its oxides are harmless for the most part (boraxes). If you measure the composition of "dust" particles, you will find boron as one of the major components besides silicon dioxide. So your are breathing these Boron containing particles in whether you realize it or not.

I am amazed they are using sapphire (ruby) or even diamond as a cantalever material. Besides the cost, these are very brittle and fragile materials.

Berylium is toxic if it is inhaled only. Thus you can have Be tweeters and so on because the Be does not become airborne.
Dhl93... I used to work in the Jewelry business and have a GG. Niether Saphire or Diamond as a crystal is particularly " very brittle and fragile." How many Diamond rings have you seen break apart? Diamond cantilevers must be the crystaline form to be called "Diamond" otherwise it is just carbon.

It is fine Berylium particles that are toxic. These get lodged in the lungs and will cause berylliosis a chronique lung disease. Small dosages appear to be sufficient to cause the disease, i.e. exposure to concentrations in the range of 1mg/m3 of air.

This is a serious issue in the mining at metals industries where the beryllium is mixed in trace amounts with other less toxics dusts.

As for exposure to a cantilever made of beryllium, I would not worry.

All this expertise is less impressive in the internet era than it once might have been. We can all Google. It might be more fun to get back to discussing cantilever materials and their effect on LP reproduction. (I apologize to all for starting this sidebar about toxicity.)

Mechans:

Diamond and sapphire are extremely brittle, in that you cannot bend or flex them without breakage. I did not mean they were not strong materials.

In a long needle shaped (ie length>>>diameter) structure like a cantalever, they would be very fragile. As used in jewelry in bulk crystal form, of course not.

In a cantalever, they are probably attached to an elastomer of some sort to allow flexing and movement. This allows some degree of freedom but I still suggest that these must be handled with the utmost care.