Some nitpicking on clay and sepiolite. From the geological point of view Clay and sepiolite are not to be equated with each other. They are totally different in respect to their properties.
Clay is a unique combination of the clay minerals kaolin, illite, chlorite, sepiolite, and smectite. It’s a heterogeneous mixture of those elements. It needs to be burned at high temperature to keep the hardness and shape like clay pipes, pottery… do.
And clays are much cheaper, I like mine,
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Sepiolite is a mineral with a characteristic needle shaped crystal structure. “It is a rare mineral with the chemical composition Mg8[(OH)2| Si6O15]2· (4+8) H2O and thus chemically a water-containing magnesium silicate with additional hydroxide ions. According to its crystal structure, it belongs to the phyllosilicates.”