e/Ninja rocks

Information
has gloss	eng: Ninja rocks are broken shards of spark plugs. Since they can quickly and almost silently fracture the glass windows on most cars, ninja rocks are increasingly the tool of choice in "smash-and-grab" auto burglaries. They have no traditional association with the ninja or ninjutsu, only being named such due to their "silent but deadly" function in burglaries.
lexicalization	eng: ninja rocks
instance of	e/Ceramic materials