These are really great questions that show that you’re doing good research!
Our MCHA is grass-fed New Zealand bovine (cattle) bone that’s produced by a pharmaceutical company that supplies many vitamin companies with MCHA to use in their vitamin supplements. We intentionally choose not to use nanoparticles in any of our products, so our MCHA is not nano-sized. Instead, it’s mechanically powdered/milled to the finest size that our production team is able to make, which ends up being around 200 mesh / 72 microns. That size is much larger than nano-sized particles, but it’s small enough to mix with our saliva and help support the body’s ability to remineralize our teeth.
Because it’s a ground product, the particles are not the ‘needle’ shape that’s concerning with nano hydroxyapatite (HA) products. To our knowledge, there is no issue at all with the shape of micro-sized HA particles. However, it’s excellent that you checked on this, because it’s our understanding that the needle-shaped nano-HA is potentially problematic (which is one of the reasons why, for us, nano is a no-no).