Choice

The gem that chooses: green by day, raspberry by candlelight — one stone, elected twice.

Alexandrite · The Law of Prototype

Family: Chrysoberyl (BeAl₂O₄) coloured by chromium
Hardness: 8.5 on the Mohs scale
Colour: Teal green in daylight, purplish red under warm light
Signature: The strongest colour change of any gem — 'emerald by day, ruby by night'

The stone read as the word

Alexandrite transmits both green and red and lets the light decide which one you see. Nothing in the stone changes; the choice is made at the moment of viewing. It was found in the Russian Urals in the 1830s and named for the tsarevitch on the day he came of age — a gem discovered on a day of election.

It is rarer than fine ruby because chromium and beryllium almost never occur together. Real choice is scarce for the same reason: it needs two things to meet that usually never do.

What it is carried for

Carried as the stone of decision — the moment a thing is elected rather than allowed.
Held for adaptability without loss of identity.
Worn by those who must act well in two very different rooms.