Big time when I was a kid. mainly crystals and fossils. Also sea shells. Rock crystals, amber, ammonites and trilobites were my favorite. Spend way too much of my pocket money on this stuff back in the day. Still have like 2 cabinets full of it.
I think halved and polished ammonites make great display pieces and quartz still fascinates me. Only gems I work with now are synthetic and in watch & clock movements. Pieces from the early 20th century and before still used natural stones, distinguishable by their paler color.
They act as bearings. Modern synthetic corundum combined with the glas-hard mirror polished steel of the axle creates an excellent friction coefficient. This has been done for hundreds of years now and when properly maintained a well made movement can function almost indefinitely. Recently saw a precision pendulum clock with a pendulum rod made of fused quartz (lower thermal expansion coefficient then even Invar). I had the same idea some years back but wasnt sure how to suspend it or how to attach the regulating nut. You cant exactly cut threads into quartz glas. They ended up suspending the rod on two blades which are balanced on extremely flat plates made of agate. The pendulum loosely slid onto the rod and friction fitted was a threaded steel tube with the nut over a roughened part at the bottom of the rod. Quite fascinating and all hand made.
Still think the Zerodur balance is a good idea, some High-horology maker should get on that.
I've been collecting fluorescent minerals for a long time. Some of them are just jaw dropping under the right type of UV light. My favorites are the Willemite-Calcite-Fluorite rocks from the Franklin, NJ mines.
As a roadway inspector we unearth all kinds of stuff from time to time.
My favorites are small river gravel simply because it's a grab-bag assortment that many times have fossils of a really old twig or other small object attached or different mineral compounds fuzed together in a rock about the size of a billiard ball or smaller.
Where I live there is a combination of deposits from the ice age melt, prehistoric volcanic activity and an old ocean bed so there is a smorgasboard of things that are uncovered from time to time ranging from gems, to fossils to military waste going back to when Spaniards explored the "new world" and found pyrite.
One area is a small section of what was attached to Africa that is squeezed against what was once the eastern edge of America. There's a fault line that separates north bound and south bound I-95 for miles and miles in both directions. That is the joint where the two met each other so long ago. Underneath the surface we see is a combination of soils once way up in the Appalacian mountains and deposits from a gigantic mud wave caused by the meteor said to have created the Chesapeke Bay. All laying over top of what used to be under water once upon a time.
When I lived at a place called Buffalo Junction, one day my son and I were looking at rocks along the edge of Buggs Island lake and noticed what looked like a row of neatly placed rocks all the same shape. All oval shaped that appeared to have been sliced like a loaf of bread or a 50 foot long sausage roll. It was the spine of a dinasaur!! I contacted all kinds of people about it but nobody seemed to care. "oh it's just rocks" they all said.
The lake ends at the John Kerr dam. Buggs Island lake feeds Lake Gaston. The water feeding Lake Gaston is regulated for consistant height so Buggs Island lake raises and lowers in order to keep the level of Lake Gaston constant. That raising and lowering of the lake caused the dinasaur spine to wash into the lake and by the time I found an archeologist interested in what we found the bones were all scattered about. I left Buffalo Junction before any information was obtained about the ancient reptile but I did bring a few of those "sliced rocks" back to my home town.
I was living in a place where population was in the dozen people per square mile. It seemed nobody around wanted the attention so everybody I spoke to just dismissed it as "rocks". I mean park rangers, local geologists etc. Their claim to fame was when Buddy Ebson (Jedd Clampet) stopped at a repair shop for a car repair one day.