I asked my mom if she had some decorative glass marbles, which she said she had, and of which I could have some. Turned out they where green! Perfect! =D I put some in a piece of cloth and gave them a good clobbering after which they turned out like the shattered pieces of glass in the pictures.

Jerodar (Jeroen) convinced me that it can actually pass for a comet shard because according to him all debris from meteorites is sort of buffed by the intense heat that develops through friction when the meteor enters the atmosphere. Also, the impact might Nevertheless I think jagged pieces of wyrdstone would look really cool too (like Ashton’s), maybe even cooler. For now I’ll settle on this.