Onyx & Obsidian
Onyx - rich, glossy black, and Sardonyx - Glossy black and white. Obsidian, equally stunning glossy black.
Black Onyx is a cryptocrystalline (micro-crystalline) form of quartz, and is characterized by taking an extremely high gloss. Onyx has been used as a decorative stone for centuries, and was popular with the Greeks, Romans and Egyptians, and is mentioned in the bible. Onyx is from the word that means "claw" or "fingernail." The story goes that Cupid trimmed the fingernails of Venus while she slept, and left the parings scattered on the sand. The Fates turned the trimmed nails to stone to protect the divine Venus. It's quite probable that the term onyx referred to all colours of onyx - the pinkish/reddish/whitish stones could have easily resembled fingernails or claws - but these days - we tend to think of onyx primarily in it's black form.
Sardonyx - also known as Black Line Agate - is a dramatic black stone banded with crisp white lines, translucent bands and the occasional venture into the brown and cream. It is a variety of chalcedony (kal-SED-oh-nee) and is found all over the world.
Obsidian is a handsome black, glossy volcanic stone. Obsidian is a natural "glass" - formed in the heart of the volcano and belched out to cool and solidify quickly. Lava stone is also a volcanic stone, usually rougher in texture.
When rock is molten in the ground, it is called Magma. Once it leaves the ground - it is Lava. Lava comes in three consistencies - thin and runny (Mafic), thick and gooey, (Felsic), and some that is somewhere in between, called, less interestingly - Intermediate Lava. It is the thick and gooey stuff that we are concerned with here - the Felsic lava - which has a higher content of silica, and when it cools rapidly - it becomes that glossy black stone we know as obsidian.
Snowflake Obsidian is the inclusion of small, white, radially clustered crystals of Cristobalite to give it the snowflake pattern.
Obsidian is pretty cool stuff, and has been in use pretty much as long as humans have been picking up shiny rocks and hitting things, which is, essentially - always. It has been used as tools, knives, arrowheads, etc., since long before recorded history - as when it is prepared correctly, it is sharper than steel.