NORTHWESTERN OHIO : CALCITE , DOLOMITE AND FLUORITE 1
Calcite is by far the most abundant mineral in the Devonian rocks at Pugh Quarry. The large crystals, from 5 mm to 10-15 cm long, are predominantly brown with wide variations in hue and intensity. The small crystals, smaller than 5 mm, range from colorless to gray-yellow to pale yellow. Both large and small crystals consist almost entirely of scalenohedral forms (dog-tooth spar habit). The most common and most easily recognized type of twinning in the large crystals is on the (0001) plane. Both dolomite and fluorite are minor minerals at Pugh Quarry, although fiuorite is found in all parts of the Quarry. Dolomite crystals occur as secondary encrusting material and are most common in vugs. OHIO J. SCI. 79(1): 24, 1979 In this third paper on the mineralogy of Pugh Quarry, calcite, dolomite and fluorite are described. The quarry is located in the SW3^, SW^, Sec. 6, T.4N, R.9E in Milton Township, Wood Co., Ohio. Its sulfide mineralization, including marcasite, pyrite, and sphalerite has been previously described (Parr and Change 1977, 1978).
BLUE JOHN FLUORSPAR
Summary The paper presents an account of the mineralogy, geological occurrence and history of the blue and white banded fluorspar found near Castleton in Derbyshire. Blue John is shown to be a fluorspar, coloured by bituminous inclusions, deposited as cavity-linings and replacements in Carboniferous Limestone of reef and massif facies. Alternative hypotheses of the cause of the colouring in Blue John are discussed. Lying more or less parallel to the bedding of the limestones, the deposits are in pipe-veins rising up the flanks of a pseudo-anticlinal structure formerly covered by impervious Namurian shales, which now outcrop only round the flanks of Treak Cliff. The relationships between Blue John and the associated minerals (calcite, barytes, galena, pyrites and quartz) are described, and an account is given of the history of the use of Blue John and the methods of manufacturing ornaments. Reasons are given for the conclusion that the story of the use of Blue John by the Romans is without foundation.
Shape and surface texture of molten droplets deposited on cold surfaces
When a molten droplet impacts on a cold surface, the interaction between solidification and fluid dynamics can lead to different shapes and surface textures of deposited droplets. This article presents an experimental study on deposition of small droplets (39 μm diameter) of molten wax ink on solid surfaces. Our results show that both the final shape and the surface texture of deposited droplets are extremely sensitive to deposition conditions, which include initial temperature of droplets, type of substrate surface and distance between substrate and printhead. Different surface textures are observed and shown to depend on the thermal and flow histories of ink droplets during the process of impact. A test using crystalline wax reveals crystallization as one of the major factors in determining the final texture.