one of the patrons of Quark's bar on Deep Space Nine had pure liquid latinum in his stomachYes. As seen on DS9: Who Mourns for Morn?, latinum in its natural state is a gray liquid that looks like mercury.There is, at least, Latinum is a substance that exists outside its gold substrate. In the DS9 episode "Who Mourns for Morn?", the character Morn kept the latinum close at hand (in his second stomach) while leaving the relatively value-less gold in a vault for others to try and steal. As a side-note, the latinum in his stomach is what caused his hair to fall out!yes, in Who Mourns For Morn(DS9) pure liquid latinum is shownPlain latinum is a liquid metal. It is gold-pressed to make it easier to handle, and separate it into its denominations (slips, strips, and bars). Morn once swallowed a great deal of liquid latinum and kept it in one of his stomachs.
I don't think it's ever been mentioned being pressed in something other than gold, or if they've ever defined what "pressed" means. I would assume it means either stored inside the gold, or alloyed with the gold to make it solid.
Gold "pressed" latinum is latinum wrapped in a gold foil. The gold acts like a wrapping, think of a candy bar, with the latinum at the middle
I believe there was also an episode (may have been a book) wherein a planet is visited by the crew (including Quark) and he is amazed to "smell" an incredible amount of latinum in the area. Digging with his hands, he finds the ground saturated with latinum; and it may have even rained latinum there.
Also, on the "pressed" issue, in the same episode mentioned above (Who Mourns for Morn?) Quark can be seen entering the container of latinum bricks, and breaking their empty shells apart. Some are clearly seen to be hollow, as the liquid latinum has been removed. There may also be some method of alloying employed in the bricks' construction, as they appear to crumble in Quark's hands when he discovers that they are empty. (I believe he 'tings' two of the bricks together and they don't make the expected sound; in fact they even break apart.)