Can you cast Magic Stone on 3 pebbles as a bonus action, throw a stone as an action, and then on your next turn, throw the 2 remaining pebbles?
That is, throwing the first pebble as your action and the second as your bonus action, using the Two-Weapon Fighting rules (PHB pg. 195; emphasis mine)
When you take the Attack action and attack with a light melee weapon that
you're holding in one hand, you can use a bonus action to attack with a different light melee weapon that you're holding in the other hand. You don't add your ability modifier to the damage of the bonus attack, unless that modifier is negative.
If either weapon has the thrown property, you can throw the weapon, instead of making a melee attack with it.
"My Reasoning" for the question:
I know that an attack is an' action. The issue is, if after throwing 1 (assuming you used that turns bonus action to cast magic stone), on your next turn could you dual wield the remaining 2 stones and throw both? (per the general two weapon fighting rule from chapter 9)
Seeing as there is no, individual, entry for "pebble" and/or "stone" (making it an improvised melee weapon?) & it's 100% considered "thrown" (or used as sling ammo):
Could the magic stones also be assumed to be "light" (like a dagger, light hammer or handaxe is?
Seeing the limited use of bonus action's spells when attacking ranged as a Druid: Magic Stone, Shillelagh, and Healing Word, as options. None are "direct attacks".
Especially before level 5, when Produce Flame and Create Bonfire outpace Magic Stone as ranged attack options, being able to "dual-wield" 2 Magic Stones would be a doubling of potential damage output at range, mainly for druids levels 1 to 4.
(Side note: I have melee handled, dual-wielding a Shillelagh'ed club with an off hand scimitar. It's pre-level 5 ranged options I hope to expand.)