Unless you’ve been living under a rock, chances are you’ve seen at least one of the painted variety popping up in your social news feed.
But what exactly is going on?
Painting rocks is just the first part in a new-ish craze which borrows from the colouring-in trend of mindfulness, treasure hunts and a real-life version of “how far can this social media post go”.
To start, people take a regular rock – something that fits in the palm of their hand – and paint it.
It’s then covered in a varnish so that the colours don’t run in the rain and to protect it from being outside.
Next, the painter hides the rock somewhere outdoors in the hope someone will chance upon it.
On Twitter, @Periwinkledink, a student at Shasta College in Redding, California, found a rock outside her campus library. She liked the little rock so much she decided to hold on to it.
She said: “The back of the rock had a paper that said to post it in a Facebook group, which I did.
“It also stated you can keep or re hide the rock, I decided to keep it because I was having a hard day and it made me really happy.”
People tend to include a hashtag in their rock artwork so that if the picture is shared on social the original painter can follow where it turns up.
Finders can choose to leave the discovered rock in situ, claim it for themselves or re-hide it somewhere else.
Kathy Fournier, who lives in the US state of Washington, started the Twitter account APaintedRock in April to share details of her own creations, plus rocks she has found.
She first found out about the craze on Facebook but was keen to publicise the trend on Twitter.
She said: “I just wanted people to know that they could participate if they don’t have Facebook or Instagram.
“I’m always dabbling in random crafts, but without an outlet for my hobbies I tend to lose interest and move on.
“Leaving rocks for others as a sort of random act of kindness instantly clicked and I enthusiastically embraced the trend.
“I tend to get depressed but painting gets me out of my head and focused on something else. With the painted rock craze, I have the added bonus of knowing, of hoping, that I’m making someone else happy, that finding my rock will bring a little bit of brightness to their day.
“I’m pretty varied about what I paint, though I suppose I lean more towards animals, especially owls.”
Recently she has also been painting rocks with a Halloween theme.
The best bit of the craze is that just about anyone can take part and the quality of the art isn’t really central to the fun of hiding and discovering a painted rock.