Ferrocarpholite was found in situ within quartz veins parallel to the foliation of the alpine metamorphic Frido, or Frido Flysch, formation (low-grade pelitic schists associated with ophiolites). It has been found in situ in only two places: 1) (BMS 48) coexisting with quartz, calcite, dolomite, chlorite, muscovite and paragonite; 2) (BMS 163) almost pure, with a little quartz. Macroscopically the mineral is indistinguishable from an actinolitic amphibole, occurring as fibres approx perpendlar the vein; the crystals are deep or light green with similar cell parameters: deep green a 13.751, b 20.140, c 5.113 A, V 1416.0 A3; light green a 13.747, b 20.163, c 5.110 A, V 1416.4 A3. Microscopically it forms elongated colourless prisms with alpha 1.612, beta 1.625, gamma 1.631, 2Valpha 68o, pleochroism colourless-light green, parallel extinction, optically negative, positive elongation and perfect (010) cleavage. EDS microprobe analyses gave an intermediate ferrocarpholite-magnesiocarpholite, with minor manganocarpholite. Sodium, Ti and Zn are present. P-T conditions of crystallization of 4.9-4.94 + or - 1 kbar and 257-260 + or - 50oC are indicated. It is suggested that the mineral formed during a late-orogenic phase along tension joints due to boudinage where elements, mobilized during the early metamorphic phase, precipitated. -R.E.S.