Rock Flour: Primary Steps in Geology

(This is kind of long, but hopefully worth it.)

It has been many years since I last saw it, so I don’t know if it is still there, but there was a cinder-block wall separating two home properties — 7260 (Jimmy Anderson’s house) and 7266 (my house) on West 90th Street, in the community of Westchester (properly in the city of Los Angeles), California. (If you go there and see it, let me know.)

The top of the wall had a slight crown to it (which we, in parts, rendered nearly flat again). Jimmy and I were about 4 years old at the time. We had other things we liked to do, but this was one thing we did often — much to the chagrin of our parents, who thought there must be something better that we could do with our time.

It was on the workbench of this wall that we learned (and relearned) important lessons in geology — particularly, that some things are harder than other things (rocks mostly, but not entirely).

Now, before I go on to explain this, I know you’re already feeling quite impressed that we were such astute devotées of geology at such a tender age. Yes, it’s true, but it’s not quite as impressive as it may seem initially. Read on.

We had larger rocks (the crushers/grinders — these were prized possessions whose useful life spanned many sessions) and then we had a multitude (seemingly endless supply) of smaller rocks (the crushees/grindees). We were tool-users. We used the larger rocks to smash and crush the smaller rocks (usually, though sometimes our fingers, too — more lessons learned). Sure, there are textbooks full of knowledge in the form of words, numbers, charts, tables, graphs — all describing hardness scales and ranking various substances relative to each other. But where’s the thrill (risk, exhilaration) in that? Sometimes (especially to a 4-year-old), book-learning only goes so far and you just have to get your hands dirty and experience the reality first-hand. I dare say the lessons learned in this mode stayed with us longer. We learned the concept of entropy (the tendency for things to go from a state of order to a state of disorder) well before we learned the word.

We developed a preference for the whiter (almost translucent) rocks as crushees (as I think back at it, I believe these were of some quartz-like composition). There was an uncommon satisfaction that came from the sound, feeling, and appearance of these crushees as we wielded our larger rocks on them. (I wish the English language were rich enough to have onomatopoeia for the sounds we heard. The word “thud” is only the crudest approximation and “Shrempfszzz”, while considerably closer, is not actually a word.) On the first blow, typically, the crushee would break into 2 or 3 pieces, then we would isolate one of these pieces and deliver more focused blows. Eventually, the rocks would be reduced to sand with our primitive banging movements. Not content to leave them in such a state, we would then apply those same crushers (but with greater deft) in a grinding movement (not unlike how we later learned that the Native Americans would grind maize into flour), and really work that dust into finer and finer flour. When we felt like we could make no more discernible difference to the state of these rocks (or would otherwise get bored with the current batch), we would use our hands to brush the rock flour onto either side of the wall, effectively clearing a spot for the processing of the next crushee. And, it was as a result of this last act that I incurred some of the gentle wrath of my father.

You see, the rocks were not uniformly reduced to flour. Some larger bits remained (we weren’t pros at this). And, from our occasional failed attempts at crushing darker rocks (which were often much less yielding to our powerful blows), we had still larger pieces of debris that got brushed off the wall. Brushing onto Jimmy’s side of the wall caused no problems — it was just sand there anyway. Brushing to my side, though, was a different story.

We had a grass lawn that went right up to that wall. Weekly, my Dad would mow that lawn with his power mower. When the mower encountered the debris, the larger pieces were transformed into wicked projectiles, with potential to wreak havoc with the nearby windows, wood fence, plants, and (of course) Dad’s legs. I never saw first-hand the destruction caused by my habit, and I don’t know that it ever materialized, but the potential was effectively communicated to me, and I haven’t forgotten the lesson in all of these years.

Now I have my own lawn, and I have children old enough to do the mowing. There are no rock walls adjoining my property, and no rock flour (coarsely ground or otherwise) in the vicinity. But there are other things (larger rocks, bricks and pieces thereof, and sprinkler heads) which present similar hazards while mowing. The sounds of the a mower blade hitting one of these things has a profoundly strong association for me (again, where’s the onomatopoeia?). I’ve heard it plenty of times, but I still wince whenever I hear it. The immediate “wicked projectile” danger is always near the top of my thoughts when I hear this sound, but the more menacing thought (which lags by only a couple of seconds) is the prospect of having to suffer the cost in time and money to replace a sprinkler head.

We’re often motivated by carrots and sticks. Although the sticks (or stones, as the case may be) have changed somewhat, there remains great motivation to not hear that wince-inducing sound when the lawn gets mowed. Because of the imprinting experience of my childhood, I’ve probably erred too far on the side of caution, and have precluded my children’s opportunity for such profoundly educational experimentations in geology. Somehow, I think they’re compensating in other (yet to be discovered) ways.