Top: example of a convex hull continuum (blue curve) applied to a smoothed version of the spectrum of one pixel in grain C0093 (black curve). The spectrum is normalised at the reflectance value at 2.6 µm. The interval used to define the continuum in this example is 2.50–3.33 µm (4000−3000 cm⁻¹). Bottom: Example of a resulting fitting curve (red curve) applied to the same spectrum. In this example, the interval 2.66–3.20 µm (3765−3125 cm⁻¹) is used to perform the fit. The four individual Gaussians used for the fit are shown in purple, pink, orange, and yellow.