Rocks

[Bod ...]

Sedimentary rock - one sediment on top of another - ash, maybe. Iridium if it's from the big meteor!
metamorphic - crystallization at specific temperatures
water/carbonates going into cracks can give a white stripe, etc...
Also humbugs and liquorice allsorts.

I'll do rocks in my next life.

Why is it that one beach will be sandy and another near by will be of the pebble sort. ?

 

[Mottie]

Rock collectors.

 

[Dork Lard]

Why is it that one beach will be sandy and another near by will be of the pebble sort. ?

It's (simplified) to do with the energy in the waves. More energy = pebbles, less energy = sandy.

 

[Dork Lard]

Picked up a lump of sea coal off the beach near Whitby, thought it would look nice next to the miners lamp on the hearth.

Years later one of wifeys mates on hearing its origins did all the tests & it's a good job we didn't burn it 'cos it's an unusually large piece of good quality Jet & worth £2k'ish !

 

[Ihavenojob]

The threads about Rocks not shampoo.

Here's one that won't need the 2nd item in your quote