Ethereum rocks — and so does Ether Rocks, a nearly four-year-old “pet rock” project for the second-generation blockchain that is experiencing a surge of interest and skyrocketing prices.

There are only 100 rocks in existence, and lately they’ve been selling for low six figures. Not bad for a low-resolution grey JPG.

“These virtual rocks serve NO PURPOSE beyond being able to be brought and sold, and giving you a strong sense of pride in being an owner of 1 of the only 100 rocks in the game :),” reads the Ether Rock website.

The rocks were created via a smart contract deployed December 25, 2017, that used a “bonding curve” — a hot topic in crypto since being popularised as a pricing algorithm used by Uniswap and other decentralised exchanges.

Basically, for each rock minted, the price got slightly more expensive.

The first Ether Rock appears to have been minted on 26 December 2017 for 0.0999 Ether – US$289 at the time. Only about 20 more rocks were sold in the first three years of the game’s existence, for between 0.1 and 0.362 Eth. About 10 more were purchased this year for up to 1.445 Ether.

Then last week there was a rush on the remaining rocks, shortly after a rush on the CryptoPunks, the first-ever NFT project that involves pixilated avatars. They’ve been selling for millions at Soetheby’s and the weekend before last, someone spent 2,700 Eth (US$7 million) on 88 Cryptopunks.

Well, if the first-ever set NFTs are worth millions — then surely the second-ever set of NFTs are worth tens of thousands?

That appears to have been the thinking, with roughly 70 rocks minted within days for between 1.2 and 10 Eth (US$3,500 to US$29,000).

Lately they’ve been changing hands for around 30 to 50 Ether (US$87,000 to US$131,000).

One crypto buff posted a tweet-thread saying spending US$46,000 on a virtual pet rock might be his best investment since getting into crypto.

On the rocks’ website, several were listed for sale for over 400 Ether (US$1.1 million), with one listed for 5555 Eth (US$16 million) and another at a fantastical 626,262 Eth (US$1.8 billion).