Main Crater, Iodake (Iwodake; Ioudake), Satsuma-Ioujima (Satsuma-Iwojima; Iou island), Mishima village, Kagoshima Prefecture, Nansei Archipelago, Kyushu Region, Japan

Description: Green to dark-green elongated, sometimes acicular crystals of good luster and well-developed crystal tips. Common in high-temperature fumaroles in the vicinity of halite crystals, in the hotter, central parts of the fumaroles.

Reference: Amir Akhavan Collection

Description: Furs of millimeter-sized white elongated crystals in crevices of a altered tephra. Associated with opal.

Reference: Amir Akhavan Collection

Habit: Massive crusts.

Colour: Gray to black.

Description: Solid gray to black crusts, water soluble. The dark color may be caused by finely dispersed molybdenite. Occurs in a zone where the bulk of the metal oxide and sulfide sublimates get deposited. Raman analysis of a black matrix with embedded tugarinovite crystals shows a curve that is a superposition of a molybdenite and aphthitalite patterns. Raman analysis done by Günter Frenz.

Reference: Amir Akhavan Collection

Colour: green

Description: Green euhedral elongated crystals inside matrix of crumbly silicified rocks around high-temperature fumaroles. SXRD by Uwe Kolitsch, NHM Vienna. SXRD: C mon, 9.72, 8.89, 5.30, 106.6 Large diopside component.

Reference: Amir Akhavan Collection

Colour: olive-green

Description: Olive-green pustules on reddish, crumbly rocks at the surface of high-temperature fumaroles. Raman analysis by Günter Frenz.

Reference: Amir Akhavan Collection

Description: Sub-millimeter sized, yellow-white to white pustules, associated with copiapite at high-temperature fumaroles. Perhaps not formed as a sublimate but recrystallized from watery solutions of dissolved sublimates.

Reference: Amir Akhavan collection

Reference: S. Hamasaki (2002) Earth Planets Space 54, 217-229.

Habit: Equant habit, typical, well-developed garnet crystals. Rhombic dodecahedra {110}, sometimes modified by {211}.

Colour: Orange, orange-yellow, green-brown.

Description: Small orange, yellow-orange and green-brown clear crystals with good vitreous luster. Well-developed and typical garnet-like crystal-shape with rhombic dodecahedra {110}, sometimes modified by {211}. Identified by Raman spectroscopy. Crystals occur in small groups inside high-temperature fumaroles associated with green pyroxenes. They can be seen in light-colored zones without sulfide and metal oxide sublimates. Raman analysis by Günter Frenz.

Reference: Amir Akhavan Collection

Colour: Colorless or white, but also intensely colored yellow, green or blue by impurities like molybdenum blue.

Description: Fibrous crusts in the vicinity of high temperature fumaroles. Colorless, white, but also colored yellow, green or blue (by molybdenum blue).

Reference: Amir Akhavan Collection

Habit: Cubes, needles, blades, as well as massive with fibrous structure.

Colour: colorless, sometimes gray and red by magnetite and hematite.

Description: 1. As solid crusts of up to 1 cm thickness with fibrous fracture and smooth to cauliform surface inside high-temperature fumaroles. The crusts are clear with a dark blue tint when removed from inside the fumarole, but turn white upon shrinking and audibly cracking in ambient temperatures. 2. As white, millimeter-sized hopper-shaped cubes, mostly intergrown as little crystal trees, covering the inner walls of high-temperature fumaroles, also on solid halite crusts. 3. As long needles (up to several centimeters), randomly intergrown, inside large high-temperature fumaroles. Description based on samples taken from fumaroles with 650 and 720 deg C on the northern inner wall of the crater (Amir Akhavan 2015, 2017).

Reference: Nitta, E., Kimata, M., Hoshino, M., Echigo, T. Hamasaki, S., Shinohara, H., Nishida, N., Hatta, T., Shimizu, M. (2006) High-temperature sublimate minerals from Iwodake volcano, Satsuma-Iwojima, Kyusyu, Southwestern Japan. Japanese Journal of Mineralogical and Petrological Sciences, 35: 270-281.

Reference: Nitta, E., Kimata, M., Hoshino, M., Echigo, T. Hamasaki, S., Shinohara, H., Nishida, N., Hatta, T., Shimizu, M. (2006): High-temperature sublimate minerals from Iwodake volcano, Satsuma-Iwojima, Kyusyu, Southwestern Japan. Japanese Journal of Mineralogical and Petrological Sciences, 35, 270-281.

Description: Conspicuous blue sublimates that cover whitish silicified rocks around high temperature fumaroles. Occasionally included in gypsum crusts, then dark blue-green. Most specimens are not stable and will pale. Molybdenum blue is water-soluble: after strong rain the blue sublimates around high-temperature fumaroles may be gone.

Reference: F. Africano, G. Van Rompaey, A. Bernard, F. Le Guern (2002) Deposition of trace elements from high temperature gases of Satsuma-Iwojima volcano. Earth Planets Space 54, 275-286.

Description: In and on salt crusts and halite cubes in high temperature fumaroles. Tiny octahedal crystals. Also as tiny, black plates, associated with a red-brown, translucent mineral, possibly hematite. These crystals may look like iron roses, as if initially deposited hematite had been reduced to magnetite. Crystal flakes are attracted by a magnet, powder XRD confirms magnetite.

Reference: Africano, F., Van Rompaey, G., Bernard, A. and Le Guern, F. (2002) Deposition of trace elements from high temperature gases of Satuma-Iwojima volcano. Earth Planets Space, 54, 275-286. Natural samples: XRD of material from a high temperature fumarole XRD-analysed by John Attard, collected by Amir Akhavan.

Description: Tiny, sub-millimeter sized, shiny flakes. Often embedded in silicified rocks around high-temperature fumaroles, but also as a sublimate in high-temperature fumaroles. Finely dispersed black powder in sulfate-crusts of high-temperature fumaroles.

Reference: Africano, F., Van Rompaey, G., Bernard, A., Le Guern, F. (2002) Deposition of trace elements from high temperature gases of Satsuma-Iwojima volcano. Earth Planets Space: 54: 275-286.

Colour: colorless to slightly blue, sometimes zoned

Description: Elongated to stubby prismatic or platy crystals with striation along the elongated axis. Colorless or slightly blue, with submetallic to adamantine luster (vitreous luster at very high magnifications). Translucent to transparent. Crystals are very small but well visible as sparkling groups. Identity of colorless crystals confirmed with SXRD by Jochen Schlüter, University of Hamburg (aca).

Reference: Nitta, E., Kimata, M., Hoshino, M., Echigo, T. Hamasaki, S., Shinohara, H., Nishida, N., Hatta, T., Shimizu, M. (2006) High-temperature sublimate minerals from Iwodake volcano, Satsuma-Iwojima, Kyusyu, Southwestern Japan. Japanese Journal of Mineralogical and Petrological Sciences, 35: 270-281.

Description: Botryoidal, colorless hyalite, associated with sulfur, in and around low-temperature fumaroles.

Description: Common rock-forming mineral in highly silicified rocks close to high-temperature fumaroles. Occasionally as a high-temperature fumarole sublimate in sub-millimeter sized, tapered, clear crystals, either as nests or single crystals.

Reference: S. Hamasaki (2002) Earth Planets Space 54, 217-229. Amir Akhavan Collection.

Habit: Very thin and soft flakes.

Description: Can be found close to the vents of small low temperature fumaroles in the vicinity of high-temperature fumaroles as a white sublimate. Water-soluble, hence can only be found after several days with dry weather.

Reference: Okano, T. (1962) Sassolite from Iwo-zima Island, Kagoshima Prefecture. Journal of the Japanese Association of Mineralogists, Petrologists and Economic Geologists, 47, 188-189.

Reference: Nitta, E., Kimata, M., Hoshino, M., Echigo, T. Hamasaki, S., Shinohara, H., Nishida, N., Hatta, T., Shimizu, M. (2006) High-temperature sublimate minerals from Iwodake volcano, Satsuma-Iwojima, Kyusyu, Southwestern Japan. Japanese Journal of Mineralogical and Petrological Sciences, 35: 270-281.

Description: Small solidified sulfur flows (a few centimeters in length) of yellow, yellow-brown to orange color, close to fumaroles.

Reference: Amir Akhavan Field Observations

Reference: Amir Akhavan Field Observations

Reference: Nitta, E., Kimata, M., Hoshino, M., Echigo, T. Hamasaki, S., Shinohara, H., Nishida, N., Hatta, T., Shimizu, M. (2006) High-temperature sublimate minerals from Iwodake volcano, Satsuma-Iwojima, Kyusyu, Southwestern Japan. Japanese Journal of Mineralogical and Petrological Sciences, 35: 270-281.

Reference: S. Hamasaki (2002) Earth Planets Space 54, 217-229.

Description: Lilac-brown crystals of submetallic luster covering rocks in the immediate vicinity of high-temperature fumaroles. Also embedded in sulfate-crusts colored black by molybdenite. Crystal size well below 100 µm.

Reference: Nitta, E., Kimata, M., Hoshino, M., Echigo, T. Hamasaki, S., Shinohara, H., Nishida, N., Hatta, T., Shimizu, M. (2006) High-temperature sublimate minerals from Iwodake volcano, Satsuma-Iwojima, Kyusyu, Southwestern Japan. Japanese Journal of Mineralogical and Petrological Sciences, 35: 270-281.

Habit: Acicular, in small radially grown tufts or randomly intergrown.

Colour: Colorless

Description: Colorless needles, in small tufts and randomly intergrown. Associated with garnet and green pyroxenes in high temperature fumaroles in zones with little or no metal sulfide sublimate deposition. Possibly (but not yet confirmed analytically) also on crumbly red rocks from high-temperature fumaroles associated with sulfates (copiapite group). Raman analysis by Günter Frenz.

Reference: Amir Akhavan Collection

Reference: Nitta, E., Kimata, M., Hoshino, M., Echigo, T. Hamasaki, S., Shinohara, H., Nishida, N., Hatta, T., Shimizu, M. (2006): High-temperature sublimate minerals from Iwodake volcano, Satsuma-Iwojima, Kyusyu, Southwestern Japan. Japanese Journal of Mineralogical and Petrological Sciences, 35, 270-281. Africano, F., Van Rompaey, G., Bernard, A. and Le Guern, F. (2002): Deposition of trace elements from high temperature gases of Satuma-Iwojima volcano. Earth Planets Space, 54, 275-286.