Encyclopedia of Japanese Minerals (Go to Intro Page)
by Alfredo Petrov
Minerals Starting with "Y"
"YAMAGUCHILITE"
= REE-phosphate-rich ZIRCON (qv) from Nagano-ken.
"YAMATOITE"
= manganoan GOLDMANITE (qv).
YARROWITE (yaroh-koh)
Akita: The "blaubleibender covellite" reported from the Hanaoka mine and the Kanahata mine is probably yarrowite (or spionkopite)?
Fukushima: Gozaisho mine.
Iwate: Tanohata mine.
Yamagata: "Blaubleibender covellite" reported from Akayama might be yarrowite or spionkopite?
"YOKOSUKAITE"
(or "YOKOSUKALITE") (See NSUTITE, under which name the species is now known, although "yokosukaite" ought to have preference since it was described 24 years before nsutite - 1938 vs. 1962.)
"YOSHIKAWAITE" (qv DYPINGITE)
YOSHIMURAITE (yoshimura-ishi; yoshimura-seki)
Aichi: At the Taguchi manganese mine, as a minor component of low-grade, schistose rhodonite-quartz-riebeckite ore. Lustrous brownish or yellow-brown, platy sharp euhedral crystals to 6mm (T. Watanabe collection), associated also with richterite and barium-bearing K-feldspar.
Iwate: Deep golden brown to orange-brown, sub-adamantine, bladed or platy yoshimuraite crystals, dominated by large b(010) faces, or as micaceous forms and cleavages to 5cm across (but usually only up to 7mm) (vaguely resembling lamprophyllite or astrophyllite) are aggregated into rough veins or occasional stellate groups, crossing pink rhodonite ore at the type locality for this complex barium-titanium-manganese silicate-phosphate-sulfate, the Misago orebody of the Noda-Tamagawa mine, where it is associated with rhodonite, quartz, barian microcline, aegirine and richterite, in alkali-pegmatitic rock on the boundary between massive bedded tephroite-rhodonite-braunite-hausmannite ore and hornfels containing manganoan phlogopite ("manganophyllite"), richterite and manganoan augite ("urbanite"), in folded stratiform manganese ore, contact metamorphosed by a Cretaceous granitic intrusion. Yoshimuraite is brittle and has a perfect cleavage parallel to the prism face (010), and two other distinct cleavage directions, (101) and (101). Polysynthetic twinning on (010). (RI 1.763 - 1.785; pleochroism bright yellow, orange-brown, brown; H 4.5; D 4.13.) Analysis (oxide wt%): Si 18.25, Ti 10.00, Fe''' 1.32, Fe'' 1.47, Mn'' 17.64, Mg 0.56, Zn 0.50, Ba 33.51, Sr 4.62, Na 0.16, K 0.03, P 3.98, S 5.40, and water 2.34, Cl 0.41. Not uncommon as brown platelets associated with quartz, serandite and aegirine in the Matsumaezawa orebody at the Tanohata mine, where it can still be collected.
YTTRIALITE-(Y) (ittoria-seki)
Ehime: Komenono.
Fukushima: At Suishohyama forms very dark green vitreous, thin masses up to 20cm across, sandwiched by large "lepidomelane" biotite crystals in the margins around a quartz-microcline pegmatite. (Metamict; RI 1.760; transparent pale green in thin section.) Partially altered to thorogummite (qv). May be associated with britholite-(Y) and a wide variety of other REE-bearing radioactive minerals. A lot of other elements replace part of the yttrium; an analysis gave (oxide wt%): Y group 44.70, Ce group 6.42, Th 5.25, U 3.72, Fe'' 2.77, Al 1.91, Ca 0.90, Mg 0.56, Zr 0.53, Mn'' 0.39, Pb 0.10, Ti 0.05, Si 29.91, C 0.50, water+ 0.72, water- 0.45 (S. Hasegawa anal.). Also at Fusamata.
Kagawa: Yashima (Setouchi acid volcanics? Qv Zircon).
YTTROTANTALITE-(Y) (ittoro-tantaru-seki)
Shiga: In granite pegmatite at Tanokamiyama (in one reference under the name "Mt. Taijin" Ðmisnomer or a sublocality of Tanokamiyama?).
YUGAWARALITE (yugawara-fusseki)
Aomori: In veinlets cutting weakly metamorphosed Miocene basalts at Okiura. Some of the yugawaralite is an alteration of wairakite.
Iwate: At Takinoue (Kakkonda) hot springs, as ugly whitish compound tabular crystals to 2cm, composed of 2 or 3 individuals aligned nearly parallel to {010}, forming crusts to over 30cm across, in low-temperature hydrothermal granular quartz veins in altered Miocene andesite. Crystals display large {010} faces and narrow {011}, {111} and {120}; often looking dull and rough because of an overgrowth of 0.01mm quartz microcrystals.
Kanagawa: Fudonotaki (the Fudo waterfall) at Yugawara Hot Springs is the type locality for the calcium zeolite yugawaralite, which here forms transparent or translucent colorless to whitish, vitreous, thin tabular crystals to 13x6x2mm in size, like flattened coffins, dominated by broad b(010) faces and narrow a(100), c(001), m(110), l(120), u(011) and p(111). Associated mainly with laumontite, almost filling small vugs (to 3cm across) and networks of 2 to 5cm-wide veinlets filling fractures in Tertiary andesite tuff breccias altered by hot springs. There is an imperfect cleavage parallel to the principal face, (010), which often exhibits iridescence. Occasional white filiform inclusions might be mordenite? Dehydration of the unstable laumontite frequently loosens the yugawaralite from its matrix. Minor close associates include quartz, wairakite, calcite and, somewhat more distantly, stilbite, heulandite-Ca, epistilbite and prehnite. (H 4.5, very brittle; D 2.23) Analysis corresponds to (Ca 0.95, Na 0.04, K 0.01) (Al 2.16, Fe 0.01, Si 5.59) O 16 (H2O) 4.25 (Harada, et al. (1969) Am. Min. 54, 306-309, 1483-1484). (Si-Al is only partially ordered in type locality material, unlike the completely ordered icelandic material.) The cliffs around the 15 m high waterfall are on the grounds of a religious shrine and should not be disturbed by collectors. Also further north, in the Tanzawa mountains (and extending across the border into Shizuoka-ken) Miocene andesitic-basaltic tuff and breccia, altered to green tuff, slightly thermally metamorphosed by a quartz diorite intrusion. Tiny yugawaralite crystals occur in vugs and veins, together with analcime, wairakite, laumontite, calcite, chlorite, prehnite and pumpellyite.
Miyagi: In altered Pliocene-Pleistocene dacitic tuff around Onikohbe hot springs, where specimens have been obtained from depths of 110 to 141 meters in drill cores from the Katayama geothermal wells, at temperatures of 110 C. Associated with laumontite, analcime-wairakite series, quartz, pyrite, chlorite and mordenite.
Shizuoka: Transparent, euhedral, thin tabular yugawaralite crystals to 3cm long, colorless to white, with wairakite (tiny white trapezohedra), laumontite, quartz and epistilbite (or dachiardite?) at Ohbora (Ohora), Toi, in vugs in veins from 2 to 10cm wide cutting propylitized andesite and basalt of the Miocene Yugashima formation, and very similarly nearby around the Seigoushi silver mine. Crystals are dominated by large {010} faces, with small {011}, {111}, {120}, and very narrow {100} and {001}. Some yugawaralites grow on the terminations of the "epistilbites". This locality was in a roadcut, now completely covered with concrete. In the Shimoda district, where yugawaralite crystals up to 2cm were found, similar in habit to those from the type locality, but additionally modified by tiny {032}, {102} and {301} faces, in veins 5 to 30 cm thick cutting greenstone (altered andesite). Also in Oyama-cho (Qv Kanagawa, Tanzawa mountains).
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