One of my favorite sedimentary rock features, ooids. These are small, rounded grains of calcium carbonate, usually 1-2 millimeters in diameter. 

Ooids are like coated sand grains. They form in areas where carbonate minerals are readily precipitating, such as warm, tropical oceanic waters. They need a core to start off growth, usually a sand sized grain of sediment or shell fragment. As those grains are tossed around by the waves, typically in a beach or near shore setting, newly formed carbonate minerals grow around the edges. The action of the waves rolls the grains, mostly keeping them from sticking together and allowing them to grow on all sides, forming these nice little spheres.

You’ll sometimes find entire rocks made of these known as oolitic limestones, and in fact there’s even a small town named Oolitic in Indiana (although residents always told me they pronounced the word different, with a long O sound in the name of the town).


Image credit: https://flic.kr/p/8EsGdG

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Got egg stones? 

Shoofly Oolite is an unusual soil that can be found along the Mud Flat Road west of Bruneau, Idaho. This rare soil supports a high number of uncommon plant species. The tiny round pieces of limestone found on the Flat are called ooids, known as oolite (“egg stone”) when deposited in larger formations. The oolite on the Mud Flat, known as the Shoofly Oolite, is part of the Glenns Ferry Formation and one of the world’s largest freshwater oolites.
For more fun information about BLM Idaho check out the February 2013 edition of the BLM In-Action Newsletter.

-Samantha Storms

More Mysterious Ooliths

We recently posted an article about ooliths (http://on.fb.me/1yWGLbD), and mentioned that one criteria for formation of ooids is a rather active sedimentary environment, one in which waves or currents can roll them around and around and around, and thus induce them to grow symmetrically to form their spherical shapes. 

Now imagine another environment. One where sedimentary deposition is sooooo slow that it takes ~5000 years to accumulate a single 5 cm layer. We’ve written of this environment in the past as well, the most boring environment on Earth, the Abyssal Plains (goo.gl/S8UUDq).

Now imagine – wait, this is hard. Another sort of rock in which ooids are found within formations formed from the abyssal ooze. Ummm… how can we form ooids, that apparently require an active sedimentary environment, in the Earth’s most inactive sedimentary environment?

Several speculations on how these silicious ooids could form include:
— Could there be an upwelling of current within the abyssal zone that lasts thousands of years? Perhaps near a hydrothermal field near a spreading ridge?

— Could we cheat, and say that these must have been originally formed as limestone ooliths, but these limestone ooliths were then transposed (through plate action such as near a subduction zone) to such great depths that the calcite dissolved and was replaced by silica (that is, chert?)

In the field area where this particular sample was found, there are great thick deposits of abbysal ooze (radiolarian cherts) that occur in association with spreading ridge formations. Alas, since this sample is from a tectonic mélange zone, it could also have come from a carbonate that was partially subducted into the depths where calcite dissolves…

Oh dear. I suppose there might be some way to solve this mystery, but then it wouldn’t be a mystery any more, would it? 

Please feel free to add your own speculations.

Annie R

Photo: mine (a scanned image of the rock, actually) from sample found by D. Ghikas within Vourinos Ophiolite sole mélange.

Read also to enter the mysterious world of rocks:

Just a smalltown girl, living in a lonely world

I posted this to FB just now.  I meant to make it a status update, but it grew:

Back when I lived in Oolitic, Indiana (google it), there was no mail delivery, no bank, no grocery store, and no one my age who lived in my town who hadn’t already married and had a billion children. Fun, huh? 

There *was* a dive bar called The Dog House (I can’t make this up). My friends from Bloomington called it The Dog Pound, which was likely more apt. I never went in there, as I really have no need of being gang-raped. Did I mention I was the only single girl in town?

There’s nothing famous about Oolitic. There’s a random statue of Joe Palooka in front of the Town Hall, which is where you were required to go and pay your water bill, because you couldn’t mail it in. Mailing it in would require walking one building down to the post office, leaving it at the desk, and waiting for the Town Hall employee to walk next door and pick it up. Since the Town Hall was two houses down from own (three if you count the fact you had to turn a corner to enter the front door), you can understand the rule, can’t you?

Anyway, it was while I lived in my butter-yellow, ridiculously affordable, turn of the century bungalow in fond Oolitic that inexpensive dial-up became the norm. I think I was the only person in town with Earthlink. It really did feel like my link to Mother Earth, my connection to the outside world. There were probably a handful of folks on the “posh” side of Oolitic who had AOL or CompuServe. I’m still uncertain as to whether East Oolitic has discovered the web. Yes, there was a *bad* side of Oolitic, and it was East Oolitic.

This morning I was sighing at the proliferation of email and FB statuses and other stuff to click through, when I remembered, “Hey. I’m on cable internet. And WiFi. On a Mac laptop. And I’m in the world again, with people I love, not just clicking around grey backgrounds and blue/purple hyperlinks, sorting through all the Star Trek websites to find *ANY*thing new and entertaining. I may have a ton of distractions now from writing, and it may be tough to juggle my family responsibilities with my work, but WOW, how far this girl has come since those days of sitting, head-on-desk waiting for a scratchy phone line to allow my modem access to the greater world.

I don’t regret living in Oolitic. Sometimes I miss my little butter yellow house with the lilies I transplanted and the sweet pea & roses climbing over the front porch rail. It’s okay, though. Oolitic is right where it belongs.

Are we FB friends?  Like my page here & friend me here.

Joe Palooka statue

Troll Or Derby is set in small-town Indiana.

S. Wachter, a reviewer on Amazon notes: 

For a book that deals with fairies, Troll Or Derby is surprisingly gritty. Tash’s fairies owe more to the “Good Neighbors” of folklore—beings it paid to treat with wariness and respect—than they do to Disney. There’s nothing cute and sweet about Roller Deb—she’s tough, and she’s scrappy, and she’s strong, and not above throwing the occasional elbow.

For all the mythic overtones, the dangers she faces are surprisingly believable—she fights off the sorts of dangers that any teenage runaway might face, and she does it not by evoking some magical power—for most of the book she’s not aware that she has any—but by using her courage, wits, intuition, and strength.

Kindle, Nook, all other eformats are available here.


Today, jacquelineboor and I visited the collection of megaliths known as the Rollright Stones. These consist of three collections knows as the Kings Men, the Whispering Knights, and the Kings Stone.

The Kings Men is a late Neolithic or Early Bronze Age Stone Circle. The circle consists of around 70 stones in a 30m circle, although originally it would have consisted of over 100. What is amazing about this circle is the type of stones used to make it. They are local oolitic limestone, with pitted-holes of all sizes and are covered in lichen - some of which is 800 years old. The textures and colours are amazing, and very unique.

The Whispering Knights is an early Neolithic dolmen burial chamber, like my favourite at St. Lythans. The capstone has collapsed and broken. Coins have been placed on this stone - a regular occurrence at spiritual Neolithic megaliths.

The King Stone is a single megalith, most likely a marker for a burial site. There are several Bronze Age and probable Neolithic burial sites in the vicinity.

The names for these sites come from local folklore. It is said that a witch turned a king to stone for failing a challenge, and he became the solitary King Stone, while nearby his soldiers formed a cromlech, or circle, called the King’s Men. As the witch backtracked away from the newly formed stones, she ran into four of the king’s knights, who had lagged behind and were whispering plots against the king. She turned them to stone as well, and today they are called the Whispering Knights.

If you are thinking about visiting Rollright Stones, check out http://www.rollrightstones.co.uk for a free audio tour.