As stated in the title, I am wondering if the spell Locate Object can be used to determine the location of a lead object (a block of it, a box of it, etc). The text of the spell at the end says "This spell can’t locate an object if any thickness of lead, even a thin sheet, blocks a direct path between you and the object". 

It is very clear that lead blocks you from locating an object on the other side of it, but what about the lead itself? What if you are searching for a magic item, and the DM says "The spell cannot locate the item as you feel something disrupting your sight." and you decide to instead cast Locate Object and ask to look for a lead-coated box? 

This is not an actual situation that has come up at my table, just a question that came to mind. 

I would say yes, the lead object can be located with locate object. I believe this because the lead isn't between itself and the spell. The moment the direct path reaches the lead in this case, you have the item. The spell doesn't need to travel farther and has the location, thus, the blocking properties of lead don't come into play.

This is, however, something that is probably up to interpretation to the DM.

For instance, in a story convenience argument of the opposite, the fact that the object has, or is, lead, could be used to prevent a party from finding it the easy way, and explain why an item not powerful enough to block divination spells is still having a hard time being found by people with access to magical prowess. This would likely still make sense to the players.

So, really, up to the DM for what fits in their campaign or setting.

Think of it like this: your eyes can't see through a sheet of paper, but it can see the sheet of paper. Similarly, the spell can see through lead, but it doesn't have to.

That's a fun question. Its a bit on the edge for me and would probably heavily rely on the DM. It depends somewhat on how the DM interprets "such as a certain kind of apparel, jewelry, furniture, tool, or weapon." How narrow can you get? Can you search for 'spears coated in silver?' Or just 'spears?'

I would argue that as long as you can make 'lead-coated box' a valid target for the spell, then you should be able to find it. Lead isn't between you and the target. Lead IS the target.

Though to start, I would probably argue that the spell would not reveal that "The spell cannot locate the item as you feel something disrupting your sight." You simply would not get a response from the spell, as if the object is not present.

Some might find it helpful to have the text handy: Locate Object

I think what this boils down to is how vague you are allowed to be when describing the object you are trying to locate. "Something made of lead" would not fly with me, as that is too broad - the words "particular" and "certain kind of [objects]" imply that you have to be a bit more precise. "A lead box" is in a gray zone for me. Is a chest a box? Is a wardrobe a box? A safe? An orb? A hollow figurine? I think there's an element of shooting in the dark here that gives the DM some latitude to say whether it would work or not.

I would say that you could find the outer layer of the lead, but not the inside of it. This would have the spell be effective but might give the caster a headache or something.

Yes, unless the lead in question is surrounded by more lead, but then again the spell will find the outermost lead which is unimpeded

Locate object works either on an item you know, an item you've seen or a generic type of item. Guessing you have no idea what the box looks like, so a straight locate wouldn't work. So you can say a generic lead box, but you don't actually know that that is the right answer. Even if you get a ping there is no guarantee its the right box.