[Firefoot]

Event? No
Living? No
Objekt? Yes
Limited Quanity if Object? Yes
Third Age? Yes
Second Age? Possibly
The Elessar? No
First Age? No
Is it a weapon? No
Can I hit Nilpaurion Felagund with it? Please? Go for it. (You can try...)
Isildur's Ring chain? No
Article of clothing? No
a piece of jewellery? No
people are envious for it? No
Is there more than one? No
a gift? No
Did an Elf own it? No
Did a Man own it? No
Did a dwarf own it? No
Is it made of wood? No
Would hitting Nilpaurion Felagund like that [over the head] have hurt a whole lot? Yes (If you could)
Made of metal? No
Made of Giftly material? No
The Stone of Erech? No
made of stone? Yes
owned by a hobbit? No
Mentioned in LotR? Yes
Does it have a specific name? No
Is it the stone that Pippin threw in the well in Moria? No
... or the stone that Boromir threw in the lake before the Moria Gate? No
Mentioned in other books, too? No (Not that I know of)
Owned by anyone at all? No
Did it come in contact with any of the Fellowship? No
Is it warding the country of Gondor through the Anduin? No
Is it a building? No
Is it a natural feature? No
Was it ever moved? In a way
Is it located west of the Misty Mountains? No
Can one person carry it? No
Is it located in Gondor? No
Is it mentioned more than once? Yes
Is it located east of the Misty Mountains? Yes
Or south of the Misty Mountains? Yes
is it possibal to be moved by people? In a way
Used for a greater purpose? No
East of Anduin? Yes
located on an island? No
On a Mountain? Yes
The Black Gate? No
Is it in Mordor? No

And the new question:

Is it the secret door in the Lonely Mountain which led to Smaug's lair? No