We have made magnetic susceptibility, electron spin resonance, and Mossbauer measurements on two different amphiboles, (Fe, Mg)7Si8O22(OH)2, and crocidolite, Na2Fe5Si8O22 (OH)2, which indicate that these materials are ordered antiferromagnetically at liquid helium temperatures. Amphibole minerals are characterized structurally by long double chains of linked silicate tetrahedra. The metal anions are ’sandwiched’ between pairs of double silicate chains to form long narrow ribbons relatively well separated from each other. In amosite the only magnetic species present is Fe2+. This has been confirmed for our samples by the Mossbauer measurements. The ac magnetic susceptibility measurements on oriented fibers indicate that there are two antiferromagnetic transitions in amosite; one around 22 K associated with an easy axis perpendicular to the fiber axis, and one around 7 K associated with an easy axis parallel with the fiber axis. The Mossbauer spectra support this interpretation. Both Mossbauer and spin resonance indicate that any magnetic impurities must be less than one percent.