xls size to 1.5mm
Henmilite
Ca₂Cu(OH)₄B₂(OH)₈
Fuka, Okayama pref., Japan
岡山県川上郡備中町布賀

In 1986, during a survey of the borate veins at Fuka Mine, Fuka, Okayama Prefecture, Japan, some small blue-violet crystals were observed closely associated with pentahydroborite. This new mineral was named Henmilite after Prof. Kichinosuke Henmi and his daughter Dr. Chiyoko Henmi, Department of Earth Science, Okayama University. In that find, crystal sizes were so small (maxium 0.2mm) and specimens recovered were so scarce that some mineralogical properties could not be mesured. In 1992, the mineral was found in a calcite vein cutting gehlenite-spurrite skarns at the Fuka Mine, this time as prismatic crystals up to 3mm long. This new material provided ample opportunity to completely describe the crystallography of the species .  In 2003, a new deposit was found and amazing specimens were recovered until the deposit is now almost exhausted. The entry to the mine is prohibited by the property owner. The specimen above is one of those found in early years. Henmilite is a very fragile mineral. / Mohs Hardness: 3 / Density g/cm3 / On heating the mineral at 900°C, tenorite (Cuo) and calcium borate (Ca2BsO5) appear as crystalline phases. 1986年に岡山県布賀において世界で初めて発見された新鉱物です。非常に小さい結晶ですが、マクロで撮ると美しい紫色をしていることがよくわかります。低温の熱水作用によってできるカルシウムと銅の含水ホウ酸塩鉱物で、紫〜青色の皮膜や顕微鏡サイズの微小な結晶の形をとります。