Actually, from the article, it mentions this:

> Leanne Kemp, an Australian who in 2015 founded a company called Everledger, has now encrypted the distinguishing features of 1.8 million diamonds and their provenance on a blockchain.

> More than 40 features are logged to create a fingerprint for each diamond, logging it from mine to ring.

So it seems, in the case of diamonds, they are unique enough to create a fingerprint. I'm no expert on diamonds, so that might not really work in reality.

I can't find very much information on Everledger's features process, just on the blockchain aspect, which doesn't inspire confidence. It's not enough for them to create 40 features you can fingerprint a diamond by, they have to be 40 features that are independently and consistently verifiable.

If I have to send my diamond to Everledger to verify it, I'm effectively just trusting them. Representing a physical object as a cryptographic hash for security doesn't work if the consumer can't independently verify the hash.

Surely you wouldn't hash a car?

Today we can't.

Actually I think we could. It just hasn't been implemented. (not to say it's practical).