I can’t say I’d ever heard of trovants before today, and they seem to be surrounded by weaselly-worded and indirect (“some say …”) claims that at least seem bunklike.
StartPage search results for just the word trovant (so the line below the URL is the page title as scraped by the search engine)
https://science.howstuffworks.com/environmental/earth/geology/trovants.htm
Trovants Are Stones That Seem to Grow ... Read even more