電子顕微鏡による養殖真珠の層状構造の観察-II:真珠超薄切片の直接観察

1) Ultrathin sections of Pinctada pearl without decalcifying were prepared by means of microtome using a diamond knife for direct observation of the architectural and crystalline structures of the mineralized tissues in molluscs. 2) The essential structure of the nacre in pearls was representative of alternating layer of elemental mineral lamella and organic membrane, the former being about 0.24-0.50μ and the latter less than 0.03μ, in thickness. 3) Ordinary accumulation of several similar mineral lamellae appears to form a zonal layer which alternates obscurely periodically with other different zones. 4) The nacre of the pearl has the double fiber structure where the orthorhombic c axis of aragonite crystals is oriented almost perpendicularly to mineral lamellae.