Welcome to Planet Basalt!
You want grey? You got grey. Basalt is mainly composed of silicon dioxide(white colored), magnesium oxide(white), calcium oxide(white), aluminum oxide(white), and iron(II) oxide(black). The darker grey areas that you see on the Moon are basalt dust. If there was wind on the Moon, it would definitely be boringly covering the entire surface rather than being in concentrated mildly-interesting 'seas'.
You want simple? You got simple. Basalt is formed when silicate-heavy lava cools rapidly when exposed to the surface. Because of the rapid cooling, large crystals don't often form in it, giving a very monotonous, fine-grained texture.
You want dust? You got dust. Basalt weathers quickly compared to many other rocks, so the winds on this planet will quickly turn the surface into dust. It's good that the planet has a non-oxygen atmosphere, as a lack of free oxygen will prevent the iron commonly found within basalt from oxidizing and turning red.
You want alchemists to think it's useful? Alchemists could think it's useful. Basalt dust can be used to make a mineral wool called basalt fiber. This fiber can be used as thermal insulation, and thermal insulation isn't that interesting to the common person. However, the fact that a vocanic rock can be alchemized into fire resistant cloth is enough to get any alchemist interested.
Addition, because I forgot it needed to be more boring than sand:
You want more boring than sand? 90% of basalt is more or equally as boring than sand. The other 10% might catch on fire. Most sand on Earth is composed of silicon dioxide, which is quite reactive and somewhat water soluble. Let's see how the major components of basalt compare to silicon dioxide:
Silicon dioxide, 45-55%. About half of basalt is just regular sand, so about half is at least as boring/interesting as sand.
Magnesium oxide, 5-12%. Magnesium oxide is prized for being physically and chemically stable at high temperatures, it lowers acidity, and is not very water soluble. So, a bit more boring than sand.
Calcium oxide, <10%. Unfortunately, calcium oxide reacts with water and produces heat, so it definitely is more interesting than sand. However, it neutralizes acids and dehydrates whatever it touches, so in a way it makes other things boring. Furthermore, if just enough water was evenly added to the planet then all of the water and calcium oxide would combine and become calcium hydroxide. This chemical is used in the food industry due to "the mildness of its basic properties", which is an exceptionally boring description.
Aluminum oxide, >=14%. Aluminum oxide is primarily just used to make aluminum. Other than that, the fact that is pretty inert means that is used as a catalyst in the production of other chemicals, i.e. it makes other things interesting without becoming interesting itself.
Iron oxide, 5-14%: Iron oxide is used as a pigment because of its consistent coloration and water insolubility, so it's quite nonreactive. However, this means that it can be used to make interesting tattoos.
In summary, the components of basalt are mostly boring, with one notable exception. About 50% is just regular sand, about 35-40%(magnesium oxide, aluminum oxide, iron oxide) are used in applications where being inert is a good thing, and 10%(calcium oxide) heats up when exposed to water. That last 10% of calcium oxide could be what the alchemists are interested in, whereas normal people just see the boring 90%.