Jewelry of Elements

This inlaid gem in this Jewelry has some weak, minor magical properties.
It can be used by anyone, does not require attunement, and everyone knows about these and anyone with Arcana Proficiency can recognizes this Jewelry, as these are somewhat common magical item.
Once used, you can not use the Jewelry's magic again until 1d4+1 Long Rests have passed.
The specific type (Fire, Water, Earth or Air) is determined by the color of the gem.

Fire (Ruby)

When you touch the gem in this jewelry together with a small flammable object, a Produce Flame spell is cast which will light the small flammable object like a torch or a candle in fire.

Water (Sapphire)

When you touch the gem in this jewelry together with a container, the necklace will magically produce clean, drinkable water enough for a single person, for a single day.

Earth (Emerald)

When you touch and activate the gem in this jewelry, it produces a small bead that disolved into a weird goo when consumed. The bead will provide you with enough nutrients to feed one person for a single day.

Air (Citrine)

When you touch and activate the gem in this jewelry, it produces clean and breathable air for one person to inhale. There is enough air for one minute.

Arcane (Amethys)

When you touch and activate the gem in this jewelry, it produces raw magical energy that will allow you to cast a single first level spell that you either know or have seen within the last week.

Omni (Diamond)

Legends speak of an Omni-variant of the Jewelry of Elements, created with a powerful magical white Diamond, rather then a red Ruby, blue Sapphire, green Emerald, yellow Citrine or pink Amethyst.
The Omni-Jewelry supposedly acts as any of the other variants and can be used to provide the magical benefits of each of them.