THEY LOOK THE SAME,
BUT THEY'RE NOT!
The four black, glassy-textured samples shown above
look very similar - almost identical. But, these represent four very
different geologic materials, formed by very different processes.
At upper left is obsidian (volcanic glass).
At upper right is indochinite (impact splash
glass).
At lower left is gilsonite (naturally
solidified oil).
At lower right is anthracite (metamorphic
coal).
These three white powdery specimens look
identical. But, they represent quite different geologic materials &
formed under very different conditions.
At top is chalk (calcitic biogenic sedimentary
rock).
At lower left is diatomite (opaline siliceous
biogenic sedimentary rock).
At lower right is kaolinite (massive clay
mineral from complete alteration of feldspar).