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Does anyone know the name of this rotated, filled in, black square symbol?

enter image description here

marked as duplicate by siracusa, marmot, Kurt, JouleV, Raaja Mar 24 at 6:23

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Some packages (e.g., txfonts) change many symbols. One possibility is to use amssymb and rotate the \blacksquare symbol using \rotatebox from the graphicx package.

Depending on whether you're using the symbol as a relation, operation or ordinary symbol, you can use the following:





$a\blackdiam b$




enter image description here

Of course you can include the \mathbin or \mathrel in the macro. You can also use \mathchoice or \mathpalette so your symbol can be used in \scriptstyle or \scriptscriptstyle.

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