This actually refers to an entire order of trees that grow primarily on lava. Note that the word ‘trees’ is very much an approximation; lachnimloth are ‘organic’ in the sense that they have a recognizable life cycle, and obey universal biological imperatives. They are absolutely neither carbon-based, nor part of an oxy-nitrogen ecosystem.
But lachnimloth are still very pretty. Extremely dangerous to humans in their living form, thanks to the heat, but very pretty. It’s all due to their makeup: the various species of lachnimloth are made up of a complicated mix of glass and trace materials. When alive it has molten glass for sap and various translucent silicates for bark and ‘flowers.’
Their fruit in particular is gorgeous (and durable when cold), and would be more of a valuable trade good for salamanders and other volcano-dwelling species if salamanders had more reasons to trade with carbon-based life forms. As it stands, salamanders have discovered that adventuring parties are generally happy to take what’s essentially the equivalent of a sack of turnips in exchange for services rendered… and salamanders are always going to need services from adventurers. Everybody does, eventually.