Pete Newman is a geologist and an old friend and colleague; as an arenophile, he was not only an early and enthusiastic supporter of my idea for the book, but also provided me with some treasures from his granular collection, some of which featured as the first colour plate in the book, others of which have been the heroes of various blog posts (see below). I have been badgering him for a while for a guest post, and I’m delighted to publish it here – along with original artwork.
The Granule
Hi Mike—
Congratulations on your new job and on getting back to Jakarta! Based on my own experiences there, I feel like you’re a lucky man. Not only in general terms, but for an Oilman and Sandman like yourself, the grease and the granules must beckon strongly. When I heard that you’d be posted there, I dug out my Indonesian sand samples to see which would be different enough to interest you. You’re already aware of the unique foraminiferal beach at Sanur and the beautiful glassy quartz grains of the Toba beaches---those will be hard to top---but there is just so much variety in that country that you can’t have seen it all. Let’s see if any of the following three granule types will expand your sand catalog.
1) I believe that I’ve previously mentioned the cute little “hopper” quartz crystal grains that I found in sand bars along the Bikis River in Kalimantan Timur. Now I’ve just found some nice hand-drawn illustrations of these in my files, originals that were done by an Indonesian illustrator, and I’m attaching one here as illustration #1. (You’d be amazed how little I paid for this work, way back in those immediate post-Sukarno days). This is one of those cases where a picture is worth a thousand words, but I never got to do a geological report where I could justify using the drawings. But just imagine a sandstone where every quartz grain was a hopper crystal, how much that would enhance the porosity beyond the theoretical maximum! Yah, dream on.
2) Illustration #2 is of a sand-sized grain of uncertain identity, one from a Kaltim beach. The characteristic crystal shape and high density (sp gr >3.3) mean that this mineral shouldn’t be that hard to identify, but I was never able to nail it down (and didn’t have too many extra-company resources to consult in Djakarta). The drawing was done by me.
3) Now we come to my absolute favorite sand grain, out of what must be the thousands I’ve examined. Illustration #3 is a sand-sized glass ball, one that came from Samudra Beach in South Java. This specimen turned up in a heavy mineral study I did to determine the source area of the Cibulakan sandstones---and thus their source direction---to learn where the thicker and coarser portions of these sands might lie. (I was trying to figure out how to do acreage turnbacks of our undrilled areas. And just for your geo-interest, the answer was a mixed [north and south] source: our reservoirs have a hypersthene/glassy quartz minor [southern] component plus an abundant zircon/tourmaline/anhedral quartz component that indicates the majority of the grains came from the Sunda Shield.)
When I began sampling the south Java beaches, I found that the sea had done my heavy mineral separation for me: the swash of the waves had separated the quartz grains from the heavy components (which were overwhelmingly magnetite, occurring in beach sand layers that were pure and as much as 15” thick). But how, you may wonder, did that help me find this grain? Well, this grain and many other glass grains were actually of a denser-than-normal glass (> 3.0 specific gravity) which meant that they were mixed in with the magnetite. Using a magnet, it was easy to separate out the non-magnetic “source fingerprint” minerals---no expensive heavy liquids required! And in this residue---a tiny fraction of the total amount of beach sand---there were a number of grains of colorless to greenish glass, often in spherical form. I separated the spherical ones from everything else by rolling them downhill---just tilted our dining room table, sprinkled the grains, caught the round ones in a sheet at the bottom.
One (and only one that I ever saw) of those grains had a “tail” that was apparently drawn out when the glass was soft---this one is my fave and the one that’s shown in the attached sketch. I’d like to say that I know the origin of this li’l beauty but all I can do is suggest three possible ways it could have formed:
1) An eruption from one of Java’s volcanoes? If found on the “Big Island” of Hawaii, this little ball would probably surprise no one as some very fine glass, including spheres, is erupted there. But are those glass balls as dense as this one?
2) A microtektite? In size and shape, it bears similarities to those, and the Southeast Asia location is right.
3) A man-made product, from construction of the Samudra Beach hotel (which sits right behind this beach)?
And though I’ve recently read about glass micro-balls being created by D-Day explosions on Omaha Beach (EARTH magazine, June), I know of no record of ordnance exploding on the south coast of Java.
So, not knowing anything real about these little balls, I certainly couldn’t say that they helped me in my work. But as you know more than most, geological fun shows up in many unexpected places. Studying geology in school, how could I have guessed that it would lead me to rolling sand grains down a table while our Indonesian cook rolled her eyes thinking “What now?”
Your sandy-haired friend,
Pete
[The “hopper” quartz grains from Kalimantan were featured in a post from a couple of years ago, the Lake Toba ones as “a few of my favourite grains,” and Pete’s Bali forams in another Sunday Sand post. Plate 1 from the book - Pete’s samples in a daily pill container – is shown above together with the hopper quartz grains. Thanks, Pete, for all your help and support – and for this post!
Oh, and the sand from the D-Day beaches that Pete refers to – see also my post and article link from the anniversary.]
Beautiful drawings of interesting grains and intriguing background info as well. Thanks for sharing!
I have a potential ID for grain #3. A fulgurite: that's sand melted from a lighting strike. The May/June issue of Rock and Mineral magazine has an article with background and images of fulgurites found in upstate New York. Photos show numerous teardrop grains with a handle. I also inspected a collection of fulgurites from a lightning strike in on a farm field in northern Minnesota a couple of weeks ago and amid that collection were numerous nodules with the filaments too. I've also seen some fulgurites from the quartz sand beaches of Lake Michigan and those were clear whereas those from northern Minnesota and those imaged in the article are greenish in color.
Posted by: Kate | June 28, 2011 at 01:08 AM