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The upper half of this gypseous formation is mainly formed of the same calcareous clay-shale rock, but without any gypsum, and varying extremely in nature: it passes from a soft, coarse, earthy, ferruginous state, including particles of quartz, into compact claystones with crystallised oxide of iron, into porcellanic layers, alternating with seams of calcareous matter, and into green porcelain-jasper, excessively hard, but easily fusible.
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