Spellstones -- customized consumables [Balance help requested]

[PhoenixPhyre]

I'm running 5e in a custom world where permanent magical items are vanishingly rare (at least at this time). I plan to include various special material types (to make items out of). For spellcasting purposes, my plan is spellstones. These are naturally-occurring stones that can be refined and charged (using spell slots).

What I want to know is if the effects listed below look at least reasonably balanced (and what rarity would be assigned). Note that all of these are consumable--usually a single charge.

Spellstones
Spellstone is a quartz-like crystal that can store aether. It comes in various forms, depending on the source and the levels of refinement. Charging a spellstone consumes a spell slot--the more powerful the slot the greater the effect. When a spellstone is used, it crumbles to dust. Refining a spellstone requires jeweler's tools. Raw spellstone can be used direct from nature.

Refinement Level	Cost to make	Time to charge	Time to make	Usage
Raw	--	10 minutes	--	When thrown (40 foot range unless using a sling), all creatures within 10 feet of the targeted location take 2d6 force damage (increasing 1d6 for every level of slot above 1st). Using at least a 3rd level slot increases the radius to 20 feet; a 5th level slot to 30 feet. Targets can make a dexterity save vs the preparer’s DC for half damage.
Cut	100 gp	5 minutes	1 day	As raw, but with 1d6 extra base damage OR Store up to a 3rd level spell (as if cast by the appropriate slot with creator's save DC/attack bonus). User must concentrate as normal.
Refined	500 gp	1 action	1 week	As raw, but with 2d6 extra base damage and 20 foot radius (increasing to 30/40 ft with the appropriate level of spell slot). OR Store up to a 5th level spell (as if cast by the appropriate slot with caster save DC/attack bonus). User must concentrate as normal.

Thoughts?