Herkimer Diamonds

These are not true diamonds, but they have their own beauty. Herkimer “Diamonds” are naturally double-terminated (also called “double point) quartz crystals that can have amazing clarity (truly crystal clear). Each crystal is a six-sided prism terminated at both ends by a rhombohedron: thereby making 18 crystal faces (facets). When the terminations are equally developed, the appearance is that of a hexagonal dipyramid. 

Herkimer “Diamonds” are unlike diamonds in that the former are natural and do not require cutting and smoothing by humans. Herkimer “Diamonds” have a hardness of 7 on the Mohs Scale (note: all quartz has a hardness of 7); thus they are not as hard as true diamonds, which have a hardness of 10.

Herkimer “Diamonds” are found at and near Herkimer, Herkimer County, New York, about a 4.5- hour drive west from New York City. These crystals occur in the very fine-grained, gray-colored Little Falls Dolostone of Cambrian age (500 million years old). Dolostone is a combination of dolomite and limestone, and dolostone fizzes weakly in a 10% solution of hydrochloric acid.

The Herkimer “Diamond” crystals always occur in vugs (cavities, like those associated with geodes) within the dolostone, and the precipitation of these crystals probably took place during the Carboniferous age, about 300 million years ago. The Herkimer “Diamond” crystals need air space. Without the “air space,” they cannot form doubly terminated crystals. They do not adhere to the dolostone. They can adhere, however, to each other, but only at the end points of the crystals. Thus, they weather out of the outcrop as individual crystals. Their value depends on the their size and how clear (translucent) they are. Some of the crystals have inclusions (small fragments of impurities), which are most commonly pieces of black hydrocarbon material.

Shown below, is a tiny Herkimer “Diamond” quartz crystal (5.5 mm long and 2.5 mm wide) still inside a tiny vug in the Little Falls Dolostone. 

Below, a larger Herkimer “Diamond” crystal (22 mm long and 9 mm wide) is shown. This crystal is not perfectly clear. It has some incipient milky quartz cloudiness, which comes from microscopic inclusions of fluids stemming from when the crystal grew. This specimen also has some black hydrocarbon inclusions.

If you are ever in the vicinity of Herkimer County, you might want to stop and do your own collecting (for a fee). It is not every day one finds doubly terminated quartz crystals that are so perfectly clear.

REMARKABLE SLUMP-FOLDED BEDS

This post concerns an “eye-popping” section of extremely slump-folded sandstone beds within the Chatsworth Formation, in the Simi Hills of Ventura County, southern California. You have to see the actual beds, or see a picture of them, in order to believe it.

These slump-folds are of Late Cretaceous age (late Campanian/early Maastrichtian age, about 70 million years old). They are located on protected land.

Three images of these slump beds are shown below (a person provides the scale): the first two are essentially the same view, but the second of these two was taken under different lighting. The third image is of the same channelized flow but a several meters westward, near the lowermost part of the slump feature.

The folded/crumpled beds consist of numerous wedge-outs of sand-rich deposits (with a sandstone to mudstone ratio of 12:1). These beds filled a braided-channel, turbidite deposit in a deep-sea-fan system of a submarine middle-fan environment (see references below for all the gory details). Turbidites are deposits of sediment-gravity flows which include turbidity currents, fluidized sediment flow, grain flow, and debris-flow mechanisms. The beds were originally in a semi-liquid state, unstable, and slid down a slope.

For more details, see the following references:

Link, M.H. 1981. Sand-rich turbidite facies of the Upper Cretaceous Chatsworth Formation, Simi Hills, California. Pp. 63–70, in Link, M.H., R.L. Squires, and I.P. Colburn, (eds). Simi Hills Cretaceous turbidites, southern California. Pacific Section, Society of Economic Paleontology and Mineralogy [Guidebook]. Los Angeles, California. 134 pp.

Note:  This slump fold was illustrated also on the cover of AAPG, v. 67, no. 3, 1983.

Link, M.H., I.P. Colburn, and R.L. Squires. 1984. Slope and deep-sea fan facies and paleogeography of Upper Cretaceous Chatsworth Formation, Simi Hills, California. The American Association of Petroleum Geologists, v. 68 (no. 7):850-873, 22 figs., 4 tables. Note: See Fig. 12D for a picture of the slump fold illustrated in this present blog post. 

How And When Did Monkeys Get To South America?

Monkeys live today in the Old World (Africa and Asia) and in the New World (South America, Central America, and southern Mexico). The consensus has been that they originated in Africa, but it is not known with certainty how they managed to get to South America. You might think that the answer is they that they simply walked from Africa to South America, but the answer is not that straightforward. 

Here are the paleontologic facts: 

The earliest known fossils of monkeys are found in Africa (Egypt) and in South America (Bolivia and in the Amazon region of Peru). They are all about the same geologic age: latest Eocene/early Oligocene (about 33-35 million years ago). The problem is that there was 1,400 km of open ocean between Africa and South America at that time (and previously for a long time—millions of years earlier, during Cretaceous time).

So, that nagging question is: “how did monkeys get from Africa to South America.” The usual answer, which that has been around since the 1960s and is still in vogue today, is that African monkeys floated on clumps of forest vegetation (e.g., modestly large forested islets) that floated downriver and eventually ended up in the ocean. These clumps then drifted across the Atlantic Ocean to South America during late Eocene/early Oligocene time. The shortest distance would have would been 1,400 km, and the drifting is estimated to have taken at least 60 days. Then monkeys then would have had to transverse overland a long distance, from the eastern shores of South America, in order to reach the inland jungles of Bolivia. This widely believed “floating-vegetation theory” is commonly referred to as the “accidental transoceanic dispersal” theory. 

Another theory is that the earliest monkeys reached South America via southern North America during late Eocene time. This theory, as well as the one discussed above, are questionably indicated on the following known paleogeographic map that shows the position of South America, relative to North America and Africa during the late Eocene. The few scientists who advocate this second theory of a dispersal route via North America have proposed, furthermore, that monkeys originated even earlier that late Eocene time. For example, in Wyoming, a sparse record of early Eocene fossils that resemble marmosets (= New World monkeys) is known.

 

While you contemplate the unsolved mystery of the ancient geographic dispersal of monkeys, it is useful to give you some background biologic information to consider. Monkey are primates. Primates include the prosmians (lemurs, bush babies, lories, pottos, and tarsiers) and also the anthropoids (monkeys, gibbons, apes, and humans). Old World monkeys consist of several families, and these are referred to as the catarrhines. They are characterized by having nostrils separated by only a thin partition, and they also have jaws with two premolars. Two examples of catarrhines are the macque monkey and baboons. Old World monkeys do not have prehensile tails. Old World monkeys include both arboreal (live in trees) and ground-dwellers.

An example of a modern-day catarrhine monkey (from Japan) is shown above. Photo credit: Wikipedia, 2021.

The New World (South America, Central America, and southern Mexico) monkeys are referred to as the platyrrhines. They are characterized by having nostrils that are quite separate, and they also have jaws with three premolars. Two examples of platyrrhines are shown here: cebids and marmussets New World monkeys have a grasping prehensile tails. New World monkeys are only arboreal.

An example of a modern-day platyrrhine monkey (cebid) from Costa Rica. Photo credit: Wikipedia, 2021.

A second example of another modern-day platyrrhine monkey (marmoset). Photo credit: Wikipedia, 2021.

A relatively recently published comparative study of mitochondrial genes of primates has been interpreted as agreeing with the fossil data showing that platyrrhines split from catarrhines at around 35 million years ago. The authors of the mitochrondrial study also advocated the “floating on vegetation” theory (see discussion above).

USEFUL REFERENCE;

For an excellent article concerning evolution of mammals in South America, I highly recommend: https://dcpaleo.org/south-americna-fossil-mammals/