Why are gemstones costly articles?

For a gemstone beauty alone is insufficient, rarity and durability are equally essential properties.

Eg:- Spharlite is a stone whose brilliance approaches that of diamond but is far too soft to be of equal value

Fine garnets are far more pleasing than bad rubies. But the rubies still hold value[elaborate more on garnets and rubies]

Additionally many gems are said to have cultural and historical significance further increasing their value.

An Italian superstition holds that sapphires are used in amulets which are worn as a protection from eye problems and melancholy and what more even Mary ‘The queen of Scots’ wore sapphires in her pendant to protect from sore eyes

The labor intensive processes of mining and refinery adds to their overall value.

‘Digging grounds to find

Shiny things to be loved

Shouting ‘hard to do’

Sweating, never mind’