lava rock

This topic has probably been beaten to death but I have a very particular question. On the Lowes website they have a product called Red Lava Rock and here is the link. https://www.lowes.com/pd/Kolor-Scape-0-5-cu-Ft-Red-Lava-Rock/50040758 My question is the following, is this a crushed version...

So I bought some lava rock on amazon, and it showed up today and is essentially useless for building anything. They sent me less rock than I ordered, it showed up wet and coated in some kind of chemical that gives them a weird sheen, and the "large" lava rocks advertised are in fact pebbles...

Looking for a good source of lava rock to build some basking structures in my new setup for my turtle. (Tank hasn't arrived yet, will post pictures when it does, getting ready for now). Looked around a bit on amazon, as I'm in NYC and landscaping supply places aren't common here. Can you use...