I have to agree with anthony about lapis being a multimineralic stone rather than a pure mineral. as a consequence there are areas that are going to be very soft, especially white with calcite, and other areas that at harder. I would stay away from rouge or anything that can discolor it. the stone is porous and will take up impurities and discolor easily… depending on the quality of the stone, it may not take a high polish.
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you need to use water to keep the stone cool when cabbing and polishing… when cutting slabs for cabs, use water rather than cutting oil…the latter makes a mess… the former causes rusting so a slab cutter has to be kept clean and dry after cutting… trim saws use water… doing dry grinding and polishing risks friction heating which can cause burn marks and even small cracks…water is the best to keep the stone clean and cool when cutting and polishing. for the final steps in polishing, you have to go dry… but still be careful of heating… if the stone feels hot, it is hot…it doesn’t matter what polishing agent you use… all will cause frictional heating… even a clean felt or cotton wheel without polishing compound causes heating.
silica dust exposure causes silicosis, an irreversible lung damage… if you really want to be safe, use an N95 or N100 mask that catches 100 nanometer particles…some serptinites carry asbestos particles that are as small as 10 nanometer… grinding stones outside is preferable than inside even with ventilation.
Good quality lapis has pyrite in it… poor quality has calcite… the rest of the blue is caused by lazurite, sodalite, nosean and related sulfur containing minerals. the presence of calcite can make polishing difficult… calcite is very soft and wears away faster leaving pits and grooves…
Cobalt salts are toxic… beryllium metal causes irreversible lung damage: beryllosis… beryl itself is inert except for fine dust, which is a silicate dust… arsenic, mercury, lead, and other heavy metals shouldn’t be a problem unless you are cutting soft metallic minerals… uranium and thorium are associated in high concentration with rare earth minerals… the amount of uranium in zircon is not high enough to cause problems… even though zircons contain enough uranium that they are key geologic indicators to the ages of rocks… the oldest rocks on earth so far found are dated by the uranium/lead ratios in zircons… going back to the early archean and late hadean periods… 4 billion years ago…copper is generally non toxic… it’s an essential trace mineral for life… too much copper by ingestion causes a zinc deficiency and vice versa…
I need to add that berylliosis is NOT caused by silicate beryl but by metallic berllium. Beryllium in beryl is bound tightly to silicate. Metal beryllium causes both acute and chronic toxicity which is irreversible and caues severe lung damage. There is no treatment, Copper and zinc are essential trace elements for health. The same protein transporter in the gut takes both zinc and copper into the blood stream. too much zinc or too much copper leads to a deficiency of the other metal… taking excessive zinc supplements to treat common colds can cause copper deficiency which causes nerve damage. However, this only applies to ingested copper and zinc.
For general purposes no one needs to worry about silicosis or beryliosis as these are consequences of industrial exposure. I still would recommend doing lapidary work outside and upwind of any dust or spray, even if indoors has ventilation.,. especially if you are going to do dry grinding which is dangerous for stones due to overheating by friction,… your concerns are well taken… people who work with potentially dangerous chemicals, fumes, and dust should take precautions. Radioactive materials pose less of a problem unless the minerals being cut have ore concentrations of uranium or thorium. Heavy metals are the same… ore concentrations… that does not mean that these materials should not be handled with caution… If anyone would like to know more about toxicity, they should post me. I do know more that just a little about rocks and minerals and health… I am an associate member of the American Geophysical Union and also an MD…