Slivers

Slivers are the primary international currency among the Fractured Skies. Created during the shaving process, or the remains of a larger drained crystal that was shattered for its slivers, these shiny rocks can be exchanged for goods and services on nearly every inhabited island.
Slivers were chosen to function as the inter-island currency because of their controlled production rate, their presence on every island, and their relative light weight. As they are produced in moderate amounts during tediously slow shaving processes of Source Crystals, the currency has proved resistant to inflation, as the rate of new Slivers entering the market is as equally slow as its production. As such, it is a relatively stable currency, as the amount which enters circulation is generally equal or slower than the amount that leaves circulation (either by loss or hoarding). Slivers value is measured in weight, via grams, with goods and services being worth a certain weight rather than amount.

Manufacturing process

Slivers are created during the shaving process, in which a tool called a Source Wedge is gently hammered into a Source Crystal's cleavage in order to break off a chunk. Larger chunks are used in the construction of Sky Ships or other industrial mechines, while shavings which are too small to hold any elemental energy become slivers.

Rarity

Slivers come in a variety of colors which identifies what attunement of Source Crystal they came from and determines their worth. Each island calculates the value of Slivers differently based on their color, usually based on what elements they have in abundance opposed to what they consider rarer. Generally, islands follow the same conversion rate as coins do in other worlds (1, 10, 100, 1000), but other islands may have their own unique conversion rates.
What element a sliver is can be identified by colour:
Air: Clear.
Fire: Red, Orange.
Water: Green, Dark Blue.
Earth: Grey, White, Brown.
Rather than being measured in individual denominations like coins, slivers are measured by weight in grams. As such, scales are a necessity of business for shopkeepers, bankers, employers, quartermasters, and all manner of business-people. In game terms, simply record each gram as you would an individual coin on your character sheet (as it is assumed your character can roughly feel out the weight).
When recording Slivers on your character sheet, do so as follows:

Type	Equivalent
Earth	Copper Piece
Water	Silver Piece
Fire	Gold Piece
Air	Platinum Piece

A wise trader or adventurer in the Fractured Skies keeps track of the relative value of their slivers from port to port, as to make sure they're getting the best deal for goods and services. Ask your DM for how much your Slivers will be worth on a specific island.