Table 3.

Mineral composition of the eleven Icelandic hydrothermal samples (biofilms or MATs, mud pots or MPs, active fumaroles or AFs, and inactive fumaroles or IFs), with presence/absence notation, based on X-Ray Diffraction and Fourier Transform Infrared Spectroscopy.

Sample	Anatase	Sulfur	Pyrite	Quartz	Hematite	Natroalunite	Kaolinite	Montmorillonite	Heulandite	Amorphous silica
MAT-54								+	+
MAT-70
MAT-78		+	+
MP-74	+	+	+				+			+
MP-87		+	+				+
AF-25	+					+	+			+
AF-90	+	+								+
IF-20	+			+
IF-49	+				+
IF-66		+								+
IF-74	+	+								+