Hey.  What is this a photo of?  I was near Hill City, South Dakota and was in a silica sand mine.  I looked up and saw this on the ceiling.  As a child I may have thought, "Cool, a bumpy ceiling."  In high school I may have thought, "What are my friends doing and I don't care about this ceiling."  In college I may have thought, "I wonder over millions of years how was this deposited?"  Ten years ago I may have thought, "The flood of the Bible deposited all this silica sand in one spot due to water flow and the density of the silica in relation to other sediment in the area."  Today I wonder, "Why does this look like it belongs underwater near a beach instead of on a ceiling?"  The point is, these are all guesses.  If anyone tells me definitively what this is, I assume they are guessing.