Where can I find Lapis Lazuli pigments?

​​I think you’re asking for lazurite​ already as an oil paint, yes?   Natural Pigments makes it but it’s currently out of stock – you can email them to ask when they’ll next produce it.  Robert Doak in NYC sells a tubed Fra Angelico Blue oil paint, a name which generally indicates genuine lapis, but you’d have to write them to be sure (their online description doesn’t specify).  If you’re willing to make oil paint yourself, you can buy lazurite in powdered pigment from Natural Pigments, Kremer, Robert Doak, and various independent manufacturers on Etsy (although the latter may be hard to verify the quailty). ​ It’s not hard (albeit takes a bit more time) to make paint from scratch – there are​ many tutorials on YouTube
The purest extractions of lazurite, which have the most color, are often referred to as “Fra Angelico Blue”.​  Here’s a description of the mineral, taken from Natural Pigments’ website: 
“The name lazurite is for the mineral that is found in lapis lazuli rock, usually found only at high elevations and at few locations on the earth. Lazurite is a complex sodium calcium aluminum silicate sulfate mineral found in calcite formations. It is a popular but expensive mineral found combined with other minerals in a rock called “lapis lazuli.” Lapis lazuli or lapis for short is mostly lazurite but commonly contains pyrite, calcite and other minerals. The name lazurite means “blue rock” and is a brilliant blue with violet or greenish tints. Small crystals of pyrite are always present in lapis and their gold yellow color distinguishes lapis from a similar mineral, sodalite, and the synthetic pigment, ultramarine. The natural mineral exhibits different properties and color nuances from artificial ultramarine and is the reason why it is highly prized even today.”

I am going to try to tread lightly on this and I will not get into whose tubed lapis paints are better or more authentic other than to write that I have suspicions that at least one supplier’s product is enhanced in color and is so full of “stabilizers” that I would hesitate to call it lapis. Additionally, 16 years ago I ran the XRF analysis of two pigments that seemed to light to be what they were advertised to be. One was supposed to be vermilion and the other malachite. The vermilion contained large cadmium, fillers and only a smidgin of mercury and the malachite hate little or no copper. I will not name these producers other than to write that their companies are still in existence and that I do not believe that they have ever contributed here. My point is that there is really no mechanism in place to force a small manufacturer (or perhaps even a large one) to accurately label their products.
There, however, are a number of suppliers of true high-quality lapis lazuli ultramarine in a good range of intensity of color and particle sizes. One of the issues with lapis is that color intensity is inversely proportionate to fineness of grind. This does mean that to make a serviceable and easily workable paint that retains the blue-violet shade of blue associated with lapis, one needs to start with stones of the highest purity and depth…meaning the most expensive. There are methods to remove some of the calcite and pyrite to naturally improve color strength. The famous Cennini method is one. The issue there is that it is laborious, and the yield of the highest quality pigment is quite low. There are other methods as well including the one outlined by Michael Price in his book.
One of the many issues with very coarse pigments is that they do not store well. In tube the pigment and binder separate making a hard lump in one part of the tube and oil in the other. This is also true of such paints stored in jars. One can get around this by adding large amounts of “stabilizers” like aluminum stearate or castor wax but then the resulting paint is nothing like the historical color. The other is that very coarse pigments make oil paints that are hard to use. The old masters had to come up with strategies to get around this AND to achieve the colored effects only available using coarser pigments.
The reason I write all the above is to say, in my experience, if one wants to paint with true ultramarine (and I am only writing about lapis lazuli, not all historical pigments in general) and needs it to be the actual, unadulterated pigment, and wants a paint that does not clump up on storage, I feel that it is best to mix one’s own paint from high quality, and reliable dry pigments and oil. This should probably be made up for each painting session. One does need to make sure that the oil component is not too high or darkening and yellowing will occur.
The last paragraph is only my opinion and I have great respect for the products and paints made by a frequent moderator to this forum and other suppliers of honest historically representative art materials. It is just an opinion based on my experience.