[mia531 (OP)]

This piece of obsidian was found and given to me in Sardinia. I am sure that it is obsidian and have also been able to identify that one facet has white 'snowflake' patterns on it. The moss green blobs and the one white blob though-is it part of the stone, is it an organic deposit on top or is it just household paint splashed on it??!!

[CliffordK]

Unfortunately you only seem to have uploaded thumbnails, so we have very little detail of your images.

Lichens are common on rocks, and can come in a variety of colors, forms, and shapes, including some that are rather flat, I think.

[Bill S]

Obsidian is prety hard stuff, so and lichen, paint etc should scrape off quite easily.

[JimBob]

I  am not so sure it is obsidian  -- aparent 6 fold symmetry on one surface ?? on others. and just to fluffy