尾太の黄銅鉱 Chalcopyrite from Oppu
幅 width: 82 mm / 重さ weight: 260 g
一辺 15 mm に達するおおむね四面体に準ずる黄銅鉱結晶が黒色の閃亜鉛鉱とともに鉱脈を埋めている。石英をともない、基盤には黄鉄鉱もみられる。黄銅鉱の結晶はたいへんシャープで、いわゆる耳つき双晶もみられる。北東北の石英・銅鉱脈に典型的な産状、形態だ。黒い鉱物は表面の質感がちょっと独特で、閃亜鉛鉱っぽくない。堀秀道「楽しい鉱物図鑑」（草思社）によれば閃亜鉛鉱の「鑑定は一筋縄ではいかない」、「よく人をだます」、とある（閃亜鉛鉱の別名 blende は「だます」という意味があるそうだ）。わたしもだまされているかもしれない。
Mostly tetrahedral chalcopyrite of 15 mm in size crystalizes in a vein with black sphalerite. Chalcopyrite crystals are sharp and some form twins with "ears". The black crystals have a texture that is not usual in sphalerite. Hidemichi Hori wrote in his book that another name for sphalerite, (zinc) blende, originally meant to deceive. He warned that zincblende was sometimes hard to distinguish from other species. This example might deceive me.
This is the so-called chalcopyrite penetration twin with ears, which is common in the Japanese hydrothermal veins. This example has particularly clear striation.