Medium hard formation with high compressive strength. Such as limestone, taconite, blaize, quartzite, silica sand, basalt, granite ect.

高抗压强度的硬地层，如硬石灰岩。燧岩。硬砂岩。石英岩。石英砂。玄武岩。花岗岩等极硬岩层。

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These are generally fed by groundwater springs, and many issued from limestone massifs, such as the Atlas Mountains in Morocco.

它们通常由地下泉水供养，其中许多流自石灰岩山丘，如摩洛哥的阿特拉斯山脉。

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It is these, fossilised, that form rocks such as chalk and limestone.

也正是这些物质，形成了诸如白垩和石灰石的化石。

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Usually this layer is a soluble carbonate rock, such as limestone or its purer form, chalk.

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Touches such as earthy limestone, wooden archways, and black and white photos of Italian streetscapes will set the tone of the dining room.

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