I do not understand why, in the overworld map in exploring, Rubies (and Amethysts) are growing out of a little plant. Do gemstones on Europa grow out of plants, or was it better to draw a little plant than a ruby or amethyst lying on the ground?

Most other resources - wood, stone, quartz, to name a few - use the same asset as their inventory picture in the overworld, although there are a few exceptions, such as cuttlefish ink and vermillion. But why the gemstone plant?

Haha, yeah, and I can I grow some in my garden?

This is a rather whimsical game. The developers probably had a bit of something extra in their coffee that day...

I now have a mental picture of a gemstone garden lol

My favourite gem is a sapphire... so lots of those, some diamonds, a few emeralds, and at least one huge oval ruby plant :D

Then I'll be ready for a night on the town :D

If pearls can come from mussels, then why not gems from plants?

It is the same principle, presumably.

@Poe

Pearls come from mussels when an irritant is covered by the mussel's natural secretion. Does that mean that plants would cover the irritant in some sort of sap that hardens into a corundum (ruby)?

In this case it meant that their origin is from that part of nature (from mussels and plants), which is usually seen as more alive and sentient eventhough the final product is "only a stone".

Well, amber is fossilised tree sap...

Gems grow out of plants, this is intended :)

The guess about sap and the reference to amber are correct. We had a couple of events with a variety of gemstones that provided some information about that. 

Yellow or orange precious stone. Such stones are slowly formed by a local plant called illustria that produces a specific resin. It crystallizes in a correct geometric shape when comes in contact with atmosphere oxygen. The color of the stone depends on the minerals contained in the soil where the plant grows.

Transparent colorless precious stone. An illustria plant that produced it was growing on soil that didn't contain any impurities to color this stone. This type of plant gems is considered to be the rarest.

Will BeastEon have these too? I like the idea of beasts with some kind of jeweller or horticulture skills growing gardens of gemstones to sell later.

"Go and pick me some herbs, roses, a couple of large amethysts... and remember to polish the ruby patch for the annual Beastopia In Bloom show starting next week"

Now have mental image of beasts stealing gems from others' gardens, somehow. A source of potential drama and entertainment. Gardening can be intense...

Hahaha, like the British have their allotments, and grow flowers and vegetables on them... And steal each others' potatoes :D