Spalchac Marble

In a turn of great irony, one of Ember Hollow's greatest exports would not be possible if not for Prazigal dumping their toxic waste across their borders.
Spalchac marble was created when the highly toxic materials from an experiment created by the Prazigallic were shoved across the border into a large limestone quarry. A war ensued, naturally, and when the dust settled, there was a massive wall created from the igneous rock that formed from the projectiles launched from Prazigal. When that wall was finished and those materials moved out of the way, the Hollowites discovered that the limestone had been transformed into marble.
Well, it's been called marble. There are some scientists who disagree with its exact classification, but the name sticks regardless.

Properties

Material Characteristics

In defense of those who call it marble, spalchac marble does look exactly like more ordinary marble. It is exclusively white, with metallic threads of gold and silver running through it, and they occasional gray streak. It is smooth and easy to polish to a fine sheen.

Physical & Chemical Properties

Spalchac marble is cool to the touch, even after having been left in the sun for hours. Moreover, it has qualities that make it uniquely suitable for the creation of monuments meant to be used as focai in various rituals. Those qualities are that it doesn't automatically explode if the ritual goes badly, thus cutting down on rebuilding costs.
It is not indestructible, simply more resistant to the more unusual varieties of attacks, like giant space lasers, storm-calling rituals, time travel devices, etc. Most who study it believe that the toxic material combined with the fraught emotions on both sides of the initial conflict that created the marble served to create a stone that is determined to remain as it is.

Geology & Geography

It is only found in Ember Hollow, due to the unique combination of environment, magic, and supply of toxic waste.

History & Usage

Everyday use

Spalchac marble being extremely rare, it is primarily used by overlords looking for a stable base of operations from which to attempt to take over the world. Despite the white and silver coloring being anathema to most Evil color schemes, it has proven to be extremely useful to make a structure that can survive a heroic attack. It is also easily painted over, for those truly concerned about aesthetic.
The side of Good has also been known to create statues and pyramids and other such monuments out of it, because if a ceremony is conducted and Evil attempts to thwart it, the chance of the structure surviving is much higher.

Hazards

Some people have been known to get frostbite from handling the materials, but this is considered an unusual allergic reaction and is not common.
What is slightly more common is exposure to the marble causing headaches and temporary blindness. There's no treatment to prevent these, simply because the effects go away quite easily as long as you remove yourself from the marble, even after longterm exposure. Also, there is no predicting when exactly these symptoms will occur, or even if you are one of the people susceptible to it, so most people go ahead and risk it.
There is some debate about this, but my own personal experience has shown that exposure to the marble can cause a Deity to lose their extraordinary abilities under the right circumstances. (It is worth noting that this effect does not continue to such individuals as wizards, witches, sorceresses, and the like.)

Type

Stone

Color

White, with threads of gray, silver, and gold running through it