Opalescence

Opalescence is a simple mod that adds Opal, a new stone type that changes hue depending on its location in the world.

A strip of opal showcasing its many different hues

Features

Opal generates naturally in the underground. It can be uncommonly found in the deepslate layer below Y=0, or more rarely in the stone layer between Y=32 and Y=56. Some of the naturally generated stone will bear crystals, which can be crafted into regular opal blocks, allowing for a renewable source of opal.

An opal deposit found in a lush cave

Letting the moon shine on fully grown, but still attached to the budding block crystals lets them aqquire a new, pearlescent hue (doesn't work when moonlight is weak). These moonlit crystals can be crafted into their respective opal variant.

A small pile of moonlit opal blocks

Both regular and moonlit opal can be crafted into various different shapes. Just plop down the stone into a stonecutter (or smelt it) and choose whichever variant you like best :)

A build showcasing different shapes of opal

(1.0.4+) The opal can be made emissive by right-clicking it with a glow ink sac, or by placing it while holding a glow ink sac in the offhand slot. The glow ink sac will not be consumed :)

Emissive opal comparison

You can also make some "interesting" hues by placing a full composter under the budding opal block and letting it influence the grown crystals. Why would you do that though?

Small mod integrations

Alex's Caves:

Guano Block can be used in place of a Composter to grow Unpleasant Opal Crystals

Ars Nouveau:

Amethyst Golems can gather grown Opal Crystals

Create:

Stonecutting Opal Crystal Blocks into Opal is changed to require sandpapering instead

Farmer's Delight:

Organic Compost can be used in place of a Composter to grow Unpleasant Opal Crystals

Spectrum / Pastel:

Budding Opal can be crafted with the help of Spectrum
A specific Spectrum block can be placed under Budding Opal to grow Moonlit Opal Crystals without the need of direct moonlight

Special thanks

Kaupenjoe - his mod tutorials are an amazing way to get into the modding ecosystem. Without them this mod would not exist.
ReikaKalseki - her mod, GeoStrata, was a huge inspiration. Thank you for creating it all those years back and making me fall in love with hue-shifting blocks.