Power Stones

Power Stones
Power stones are what allow Petralists, Builders, and Stone Sculptors use to access their fantastical abilities. In The Petralist series universe ordinary rocks hold the keys to supernatural abilities for certain individuals.

Igneous Stones
These stones are absorbed in powder form through the skin for Petralists, and are activated somewhat remotely/through touch by Builders. Igneous Petralists will carry around a bag of stone powder to fuel their powers.

Granite
Granite grants Petralists moderate superhuman strength, enough to throw boulders and uproot trees, and turns their bodies into living rock. Being a living statue grants the Petralist increased durability and a temporary immunity to non-fatal injuries, such as any scrapes or even lost limbs. Any crumbled body parts or gashes in their stone bodies will painfully manifest later on when the Petralist converts back into human form. Granite at a Builder's command becomes as hard as steel.

Basalt
Basalt grants Petralists superhuman agility and running speed about that of your average car. At higher speeds basalt will "frack" a petralist's leg, growing a new joint in a painful process that allows the petralist to make sharp turns while going at high speeds. At a Builder's command a basalt stone gains a near instant increase in kinetic energy and will rapidly increase in velocity.

Obsidian
Obsidian "magnifies innate abilities" for a Petralist. This includes a temporary increase in intelligence/thought, reaction time, situational awareness, general skillfulness, and combat ability. Petralists who can tap obsidian are ninja-like and confident, and while it's not outright stated in the books it is implied that Obsidian Petralists gain enhanced agility/grace while tapping obsidian. Whether this is because obsidian enhances pre-existing combat skills or grants a agility buff is iffy. Obsidian is a vaguely defined power. However the gist of it is: increased quick-wittedness and skillfulness.

Sedimentary Stones
Sedimentary stones are absorbed through stone-to-skin contact. They are absorbed in an unprocessed state. Sedimentary Petralists will usually hold the stones in their pockets or wear them in the form of a necklace or bracelet. Builders can activate them somewhat remotely/through touch.

Limestone
Limestone allows Petralists to manipulate light and grants Builders a flashlight. When tapped or activated limestone will emit light and the brightness will increase or decrease depending on the amount of magic power being released from the stone. Petralists are also able manipulate the brightness of other light sources in the area.

Sandstone
Sandstone possesses magic healing power that can heal minor injuries or near-fatal wounds. Petralists can tap then channel that restorative energy to heal themselves or others. Builders can activate sandstone and apply the healing power using the physical stone.

Metamorphic Stones
These stones grant access to elemental powers. Petralists access them in very specific ways. Builders can use these stones to produce elemental effects such as raising earthen walls, summoning water, or shooting gusts of air or fire from activated power stones.

Slate
Slate grants access to the Earth. Petralists tap slate by putting a wafer of slate in their shoes and, as long as their feet maintain contact with the ground, they're granted a limited form of geokinesis. They're able to manipulate surrounding sand,dirt, and soil but not solid rock. Petralists are also able to draw sustenance from the Earth granting them more stamina and possibly even strength. It's even speculated that a strong enough connection with slate and the Earth may grant enhanced longevity.

Marble
Marble grants access to Fire. Petralists tap marble by placing a piece of it under their tongue, making the rock taste spicy, and granting the petralist the ability to conjure and manipulate fire. Unlike normal fire which is a chemical reaction, magical marble fire has a semi-solid property that allows it to be morphed into tangible constructs that can strike with physical force.

Quartzite

Quartize grants access to Air. Builders can activate quartzite stones that blast gusts of air.

For Petralists quartzite grants superhuman senses such as sight, hearing, and smell as well a limited form of aerokinesis. They're able to knab and direct existing wind currents, and even sometimes ride them temporarily to glide or "fall with style".

Soapstone

Soapstone grants access to Water. Petralists tap soapstone by ingesting it, typically by drinking a water/soapstone powder concoction, and this allows them to manipulate existing water in the surrounding environment. It's an pretty advanced form of hydrokinesis. Soapstone Petralists can change the temperature and state of matter of water, turning it into ice, steam, or liquid water.