I know I've seen that brand in the magz and in the mall. I am currently using bare minerals. How come you switched?

Prescriptives certainly isn't new...but perhaps their mineral line is.  I believe that Presecriptives claim to fame has always been their custom blend make-up. Here is Paula Begoun's take on this (below) but keep in mind if something WORKS for you it WORKS.  Everyone is different.
The Prescriptives account representative I spoke to was incredibly excited about this loose-powder foundation, and I suppose justifiably so, at least from a marketing perspective, because mineral makeup continues to be a hot commodity. Most major cosmetics companies have dipped their toe (or should I say powder brush?) into this profitable once-niche market.

Given there is no consistency in the mineral makeup market, each formula chooses randomly between talc, mica, bismuth oxychloride, or a mixture of all three; in this case it’s mostly mica. The twist is that it also contains amethyst and calcite (calcium carbonate, which also is used in cement and mortar and is one of the the most abundant natural minerals. Silica is the most abundant, and then there is the discussion of minerals being inorganic only…. So, I’ve reworded to avoid the issue >). “Imbued with special properties for skin” is the Prescriptives angle, but there isn’t a shred of research to indicate their claims are anything more than ideas from their marketing team.

Aside from the claims that semiprecious gems having miraculous benefits, what you do get in this product is reliable, non-irritating sun protection thanks to the titanium dioxide and zinc oxide active ingredients. Combined, these minerals comprise nearly 17% of the product’s contents; as such, they contribute to its medium, buildable coverage and somewhat opaque finish, but it also means this powder isn’t as gossamer-soft as I was expecting, although it is still silky-smooth with a dry feel typical of most mineral makeup in powder form. Dusting this on with a powder brush nets sheer to light coverage, while using a buffing brush (which has greater density than a standard powder brush) nets decent coverage and effective sun protection (a sheer dusting wouldn’t give you the sun protection). Either way, it leaves your skin with a satin matte finish completed by a subtle sparkle.

Packaging-wise, Prescriptives’ merely offers a typical loose powder jar with sifter. That means that the powder gets into the sifter area rather than being protected by some sort of closure—I was hoping for more practical, neater packaging, but no such luck. This really shines (pun intended) with the ample selection of mostly terrific shades. The high amount of titanium dioxide and zinc oxide means that most of the darker shades have a slight to obvious ashen finish, and are best avoided. The other shades to watch out for include the very pink Level 3 Cool Medium and the rosy orange Level 3 Cool Light. These shades can quickly turn orange when they mix with skin’s oil, making for an even more unnatural look. The shades in Levels 1, 2, and 4 are the best options, but give the Level 5 shades a try if your skin tone isn’t too dark. All told, this is a respectable entry that with some fine-tuning (including better packaging) would warrant a Paula’s Pick rating.

Well, as I said, the Prescriptives LINE isn't new but their mineral line seems to be.  Good luck!