Sep 202017
 

As a follow-up to our public AEG seminar last week, following are three of the PowerPoint presentations:

City of Colorado Springs Geological Hazards Ordinance, Peter Wysocki, AICP, Planning and Community Development Director, City of Colorado Springs


Requirements for the Colorado Springs Landslide Susceptibility Zone, presented by Bob Moore, P.E., Risk Management Engineer


Landslide Susceptibility in the Colorado Springs Area – Geology and History (download), Jonathan L. White, Colorado Geological Survey


Feb 192017
 

Diamonds are formed from pure carbon, one of the most abundant elements on planet Earth. Diamonds, even from ancient times, have been sought for their extraordinary hardness (they are the hardest substance known) and their brilliance, especially in the colorless transparent gemstone variety. Ironically the other form of pure carbon is graphite, which is very soft with a soapy feel and a dull gray color. Graphite is commonly the “lead” in a pencil.

A diamond's crystal structure: tetrahedrally bonded carbon atoms crystallized into the diamond lattice, a variation of the face-centered cubic structure.

A diamond's crystal structure: tetrahedrally bonded carbon atoms crystallized into the diamond lattice, a variation of the face-centered cubic structure.

The Mohs Hardness Scale of minerals starts at 1 (talc) and ranges to 10 (diamond). That does not mean that diamonds are ten times harder than talc; mineral number 9 on the Mohs scale is corundum, a class of minerals which includes rubies and sapphires. Diamonds can be from ten to hundreds times harder than corundum. Diamonds themselves vary in hardness; for example, stones from Australia are harder than those found in South Africa.

The four main optical characteristics of diamonds are transparency, luster, dispersion of light, and color. In its pure carbon form, diamond is completely clear and transparent. As in all natural substances, perfection is nearly impossible to find. Inclusions of other minerals and elements cause varying degrees of opacity. The surface of a diamond can be clouded by natural processes, such as the constant tumbling and scraping in the bed of a river.

Luster is the general appearance of a crystal surface in reflected light. Luster of a smooth crystal face of diamond is strong and brilliant. It is intermediate between glass and metal and has its own special term — adamantine.

Relative size of octahedral diamond crystals from 1 to 500 carats. Credit: Modified from Bauer, 1968.

Relative size of octahedral diamond crystals from 1 to 500 carats. Credit: Modified from Bauer, 1968.

The process of white light breaking up into its constituent colors is called dispersion. Diamonds have strong dispersion, which along with their strong luster, causes the beautiful play of colors so often referred to as the “fire” of a diamond.

Gemstone varieties of diamond and imperfections. Yellow or yellowish-brown and even brilliant yellow diamonds have been found. Very rarely, diamonds are blue, black, pale green, pink, violet, and even reddish.

The most famous blue diamond, the Hope Diamond, is intertwined with Colorado’s mining history. Thomas Walsh, discoverer of the rich Camp Bird Mine near Ouray, purchased the Hope Diamond for his wife in the early 1900s; it was later given to his daughter, Evelyn Walsh McLean who wore it almost continuously until the 1940s. The 45.5-carat Hope Diamond now resides at the National Museum of Natural History in Washington, D.C.

Diamonds, in their perfect cubic crystal form, occur as isolated octahedral (eight-sided) crystals. Many variations on the cubic form are found in are usually clear and colorless, often containing minor inclusions nature, including twelve-sided crystals and a flattened triangular shape known as a macle. Gemologists recognize three main varieties of diamonds: ordinary, bort, and carbonado. Ordinary diamonds occur as crystals often with rounded faces, from colorless and free from flaws (“the first water” [1]) to stones of variable color and full of flaws. Bort diamonds occur in rounded forms without a good crystal structure. They are generally of inferior quality as a gemstone. Carbonados are black opaque diamonds usually from the Bahia Province of Brazil. They are crystalline but do not possess the mineral cleavage found in ordinary diamonds.

[1] An expression which refers to the highest quality diamonds and has come to mean the highest quality of just about anything. The comparison of diamonds with water dates back to at least the early 17th century, and Shakespeare alludes to it in Pericles, 1607:

Heavenly jewels which Pericles hath lost, Begin to part their fringes of bright gold.
The diamonds of a most praisèd water Doth appear, to make the world twice rich.

Diamonds in the rough, note the regular octahedral forms and trigons (of positive and negative relief) formed by natural chemical etching.

Diamonds in the rough, note the regular octahedral forms and trigons (of positive and negative relief) formed by natural chemical etching.

Jan 112017
 

Regarding the Colorado Geological Survey (an article appearing in the Mining Reporter, March 1907):

We note that one of our contemporaries, in recently commenting on the University bill creating a State Geological Survey of Colorado — the bill reported favorably on by the joint Senate and House mining committee — voices in no uncertain language its regret at the “truly pitiable outcome of the effort to establish a Geological Survey of Colorado.” In a lengthy and well-written editorial, criticism is made of the proposed advisory board, particularly of the placing thereon of the presidents of the State University and the State Agricultural College; also, having the survey located at Boulder instead of Denver; of the naming as state geologist, the professor of geology of the State University, who may be a good teacher, but who, like the majority, may or may not be an effective executive; and lastly, of the paltry appropriation of $5,000 annually for this important work in a state productive of $50,000,000 and more yearly.

Exception is also taken to the naming of state institution teachers as assistants to the State Geologist, who ought to have the assistance of men less academic and having a knowledge of the exploitation of ore deposits and of the search for them.

This editorial expression, coming from a former Coloradoan, is worthy of consideration. It is in accord, in large part, with our own views, as our readers know. In addition to the criticisms made by our contemporary, we would like to emphasize another objectionable feature in this favorably reported bill, viz., the naming of any one as state geologist who is not to devote his entire time to the survey work. — from the Mining Reporter, vol. LV, March 28, 1907, no. 13, Denver, Colorado.

We’re happy to say that our current efforts to provide professional geologic information to the residents of Colorado far exceed the original scope of responsibilities and possibilities of the Territorial Geologist. But like those old-time miners, walking the mountains of this beautiful state, we also share a real passion for what we are doing.

You can find an in-depth history of the Survey and its 1872-legislated precursor, the office of Territorial Geologist, in IS-27 History of The Colorado Geological Survey (1872-1988), a free PDF download at our bookstore.


Citation: Rold, J. W., and S. D. Schwochow. IS-27 History of The Colorado Geological Survey (1872-1988). Information Series, IS-27. Denver, CO: Colorado Geological Survey, Department of Natural Resources, 1989.