Obsidian is a type of naturally occurring volcanic glass - when Obsidian has a sheen to it, it is due to patterns of gas bubbles that are trapped in layers due to the lava flowing before the glass solidifies.
Obsidian sheen is particularly good for scrying, and is said to enhance self-reflection and understanding. This makes it a good stone for mediation, as well as any time that you may need clarity or a sense of direction.
Obsidian sheen is associated with the Root chakra, which governs foundation.
Size and color may vary. This listing is for one piece.