Pure’s spectrometer uses a nice little micro-spectrometer from hamamatsu. At $298 USD on Tindie it’s not exactly the cheapest way to do spectroscopy, but it’s a tight package and ready use with an Arduino.

[Pure Engineering]’s C12666 Micro Spectrometer has applications ranging from detecting if fruit is ripe, telling you to put sunscreen on, to detecting oil spills. Like the title says, it’s based on the Hamamatsu C12666MA spectrometer, a very tiny MEMS spectrometer that can sort light by wavelength from 340 to 780nm.

Source: Earth Day: Environmental Sensors | Hackaday