A manastone is a manamaterial in the form of a crystallized chunk of elemental mana that serves as a conduit for converting pure mana into another element. Manastones are valued all around Mezia and are the only "universal" currency as they can be traded just about anywhere.
Manastones are measured by their size, which determines the mana conversion capacity of the manastone. Larger stones can convert more mana and therefore make a spell more powerful. Manastones are very valuable and sought after, especially for certain elements.
Mages usually embed their manastones into their equipment to have them close at hand for conversions, as well as making them easier to guard.
Properties
Size
Manastones are measured in terms of their size. Manastone size changes how much mana can be converted through it at one time and how long mana can be converted through it before the stone shatters. There are five standard sizes: sliver, shard, crystal, boulder, and monolith.
Sliver - The smallest size manastone. Slivers are not particularly valuable or useful, as they can only convert enough mana for a single weak spell before crumbling to dust. Those in possession of a mana sliver are usually best off just using it. Some potions use mana dust as a component, so a mana sliver of a particularly rare element may find a buyer.
Shard - About the size of a person's finger. A mana shard is potent enough to produce the mana for some very useful spells and sturdy enough to be used repeatedly, though not continuously. Shards are by far the most widely exchanged size of manastone and are accepted by almost all merchants. When a shard shatters it leaves behind 1-2 slivers.
Crystal - About the size of a basketball. A mana crystal is a significant step up in terms of spell power. Spells can be cast with more mana and sustained for a short time. Crystals are very valuable, generally only traded for expensive or bulk goods. When a crystal shatters it leaves behind 1-2 shards and 5-10 (1d6+4) slivers.
Boulder - About the size of a car. A mana boulder is powerful enough for multiple mages to be casting high powered spells through it simultaneously without putting a strain on it. Mana boulders are at the heart of many small settlements and caravans to provide the defenses for the whole group. Trading a mana boulder is possible, but there is not much of equivalent value to one. When a boulder shatters it leaves behind 1-2 crystals and 5-10 (1d6+4) shards.
Monolith - The largest size manastone. Monoliths can vary significantly in size, but they all share the property that a spell can be cast through it indefinitely without risking breaking it. Although a monolith could be used to cast unimaginably powerful spells, that is rarely the case. All known monoliths are either the center of a large settlement or embedded in a massive behemoth. Monoliths usually serve as a way to defend these settlements and creatures, rather than for offensive purposes. Even if one found a buyer for a mana monolith, they are so big they are practically immovable. Do not worry about how many boulders a monolith breaks into because nobody wants to be around when that happens.
Element
Every manastone is formed of one single element. Mages can draw pure mana through the manastone to imbue the elemental properties of the stone into the mana, thus creating elementally charged mana that can be used in a spell.
Drawing mana through a manastone is one of the most basic techniques a person learns when starting to use mana. For most, this is something they learned as a child and don't need to think too much about.
Sources
Mana Springs
Mana springs produce the greatest quantity and size of manastones on Mezia. These primeval fonts have such high local concentrations of mana that some of it crystalizes and slowly grows into ever larger manastones. The mana monoliths existing today are theorized to have been formed by ancient mana springs that have long been exhausted.
The locations of mana springs are well known and are guaranteed to contain many manastones. However, mana springs are not a major source of new manastones for use because entering a mana spring is so dangerous that returning alive with manastones is unlikely and, for most, not worth the risk.
Sometimes young and/or stupid mana hunters venture into a mana spring hoping to strike it big, but they fail to realize just how chaotic the mana within a mana spring can be. Getting deep enough to find stones large enough to be worth the journey and carrying them out without dying is a very lopsided gamble. Those who return empty-handed are the lucky ones.
Manastorms
Manastorms create a huge spike in mana density and a violent vortex of mana. Within a manastorm, pure mana collisions can cause crystallization or spontaneously convert into elemental mana. Manastorms leave behind mostly a trail of pure mana slivers, maybe a few pure mana shards or an elemental sliver too. The naturally produced stones from manastorms are not of much value.
There is another way to extract far more valuable manastones from a storm though. A mana hunter who knows how to compress mana can use the high mana density to their advantage and force it to crystalize much faster than normal. Mana hunters are reliably able to create pure mana crystals using this technique, and it has the added benefit of weakening the storm. In theory, multiple people working together to compress the mana of a large enough storm should be able to create a pure mana boulder, but that requires a level of coordination that is near impossible to pull off when faced with a sudden manastorm. Creating crystals is hard enough as is.
Meteor Shower
Manastones sometimes fall to Mezia in meteorites.