Datholite, or Borate of Silex and Lime

At Arendal in Norway, so famous for a variety of new substances, was this discovered by Esmark. Our specimens are from the British Museum, and were formerly part of the collection of the Hon. Charles Greville. The crystals are finer and larger than usual; they are short rectangular prisms, with from six to ten lateral planes, the acute solid angles of which are replaced by one or two faces, and sometimes a narrow face upon the upper edge. Sec the geometrical figure. The matrix is generally obscurely foliated Carbonate of Lime, which runs in veins through greenish lamellatcd Serpentine, but in the lower figure the Datholite Is attached immediately to the Serpentine, and has a few crystals of Carbonate of Lime coloured by Iron scattered over it. The upper figure has smaller crystals standing in many directions, with remarkable modifications shown in the right-hand geometrical outline.

It has not much lustre; internally it is nearly vitreous; fracture small, partly conchoidal; hardness superior to that of fluor. The primitive crystal, according to Haüy, is an upright prism, with a rhomboidal base of 109°. 28′. and 70°. 32′. Spec. Gray. 2.980.