"Piezoelectric (crystal and ceramic) cartridges were extremely common in low-quality record players. If you buy one of those junky nostalgia things advertised right now, it'll come with one: guaranteed. These have always been low-compliance, high output devices; generally ratty.'
Like undoubtedly everybody here, I look askance and smirk at those 'nostalgia' machines whenever I see 'em, although I do think it's pretty interesting (if unfortunate in ways) that these players have cropped up so profusely in department and discount stores over the last few years -- surely that says something about a latent demand for people to be able to play their records once again.
But I make excellent use of one of those very same cartridges in my battery-powered Numark portable that I always take along (with a pair of folding Sennheiser headphones) whenever I go used record shopping. And you know what? It doesn't sound like a crappy toy. For a plastic-bodied device that cost as little as it did, I can actually enjoy listening with this unit (provided it's thru the 'phones), and the needle doesn't sound or otherwise seem like it tears up the grooves either. Never have I heard it mistrack more than a slight bit, and most often not at all. Thing's saved me a ton of money in chances not taken, while the discard pile's become vestigal. Oh yes -- Eldartford, it is stereo, however it works. Hi fi? No. But it easily does the job, telling me everything I need to know about the music and playing condition of found records.