PC Large Eberron Shard

[Sehenry03]

Any idea of value and what it is used for?

[sireric]

You can trade them in to various collectable turn in NPCs in game. I do not remember off the top of my head who collects the larges and what all of the possible rewards are, but there are 3 different rewards depending on who you give 3 of them to. The larges are not that great because really the best thing you can get from them is an Eladrin rest shrine. The mediums go for more because you can get a gem that has 20 charges of major mnemonic enhancement.
You my also be able to use the larges in crafting but I am not sure.

[CheeseMilk]

Best use for Large Eberron Shards is to trade in for 3 Purified Dragonshard Essences for high-end Cannith Crafting recipes. These are BTA, however, so don't crunch them down unles you plan on using them yourself.

The trade-ins will net you:

-Ethereal Rest Shrine from Seld the Gray Sister (House P, Intelligence collector)
-Medium Jewel of Fortune from Bowdlin (House P, Soarwood collector)
-Kohl's Gem (just a vendor trash gem, worth like 5kpp) from Kayla Skywhisper (House P, Omen collector)

Since none of these rewards are nearly as useful as the ones from small (xp pots) or medium (xp pots and mnemonic enhancer trinkets) they really aren't worth all that much. Due to their rarity (and the fact that they should give more than they do) you'll see them for a fairly high price (~80-100k) in the AH, but they're not likely to sell, even just to be crunched. A +1 tome gives more Essences, and you can pick them up for 10k at times.