Question the Amarillo Starlight

The Amarillo Starlight is the largest diamond found by a park visitor in the Crater of Diamonds State Park in Arkansas since 1972, when it was established as a State Park, where visitors were allowed to prospect for diamonds for a nominal fee and keep what they find. The 16.37-carat rough diamond was discovered in 1975 by Mr. W.W.Johnson of Amarillo, Texas, the town from which the diamond gets its name.

I stumbled upon this image taken by Mary Caperton Morton, at the Crater of Diamonds State Park near Murfreesboro, depicting the site where the 16.37-carat Amarillo Starlight Diamond was discovered by Mr. W.W.Johnson of Amarillo Texas in 1975.

What is the largest rough diamond ever discovered in the history of exploitation for diamonds at the Crater of Diamonds Park ?

In the history of exploitation of diamonds in the Crater of Diamonds State Park in Arkansas, previously known as the Prairie Creek Pipe Mine, since diamonds were first discovered in the region in 1906, the largest rough diamond ever discovered was the renowned, 40.23-carat, Uncle Sam Diamond, discovered in 1924 by Wesley Ole Basham, and eventually transformed into a 12.42-carat, emerald-cut finished diamond with a color grade of "M" equivalent to faint yellow and clarity grade of VVS1. The rough diamond had a slight pink tone which was also visible in the cut and polished diamond. Incidentally, the 40.23-carat Uncle Sam rough diamond is also the largest diamond ever found in the United States.

Since the largest rough diamond ever discovered in the Crater of Diamonds State Park in Arkansas weighed only 40.23 carats, it follows that most of the diamonds discovered in the park are of restricted sizes. What can you say in general about the sizes of the diamonds discovered in the Park ?

The following is a list of notable diamonds discovered at the Crater of Diamonds State Park arranged in descending order of carat weights of the rough diamonds as at year 2011 :-
Information in respect of each diamond is provided in the following order :-Name of diamond/ Discoverer/ Year found/ Rough carat weight/ Finished carat weight/ Color
1 Uncle Sam; W.O. Basham; 1924; 40.23; 12.42; white.
2 Star of Murfreesboro; John Pollock; 1964; 34.25; uncut; blue.
3 Lee J. Wagner diamond; Lee J. Wagner; 1917; 17.86; uncut; canary yellow.
4 Amarillo Starlight; W.W.Johnson; 1975; 16.37; 7.54; white.
5 Star of Arkansas; 1956; 15.33; 8.27; white'
6 Star of Shreveport; Carroll Blakenship; 1981; 8.82; uncut; white.
7 Illusion diamond; Beth Gilbertson; 2011; 8.66; uncut; white.
8 Lamle diamond; Betty Lamle; 1978; 8.61; uncut; brown.
9 Connel diamond; ---- ; 1986, 7.95, uncut; white
10 Dickinson/Stevens diamond; Dickinson & Steven; 1998; 7.28; uncut; yellow.
11 Cooper diamond; Richard Cooper; 1997; 6.72; uncut; purplish-brown.
12 Gary Moore diamond; Gary Moore; 1960; 6.43; uncut; canary yellow.
13 Roden diamond; Donald & Brenda Roden; 2006; 6.35; uncut; honey-brown.
14 Lee diamond; ----- ; 1988; 6.30; uncut, white
15 Newman diamond; Newman; 1981; 6.25; uncut; white.
16 Bleeding Heart diamond; Joe Fedroza; 1991; 6.23; uncut; brownish-yellow.
17 Stockton diamond; ------- ; 1981; 6.20; uncut; white.
18 Schall diamond; ------- ; 1981; 6.07; uncut; white.
19 Cooper diamond; Richard Cooper; 1997; 6.00; uncut; brown/cognac.
20 Sunshine diamond; Bob Wehle; 2006; 5.47; uncut; canary yellow/flawless.
21 Sweet Caroline; Richard Burke; 2008; 4.68; uncut; white.
22 Kimberley diamond; Denis Tyrrell; 2008; 4.42; uncut; white.
23 Johnson diamond; Chad Johnson; 2007; 4.38; uncut; brown/tea colored.
24 Khan Canary; George Stepp; 1977; 4.25; uncut; canary.
25 Okie Dokie diamond; Marvin Culver; 2006; 4.21; uncut; canary yellow/flawless
26 Strawn Wagner diamond; Shirley Strawn; 1990; 3.09; 1.09; white.
27 Royce Walker diamond; Royce Walker; 2009; 2.93; uncut; dark honey-brown.
28 Brown Rice diamond; Glenn Worthington; 2010; 2.13; uncut; brown.
29 Easter Sunrise diamond; Glenn Worthington; 2009; 2.04; 1.09; yellow.
A perusal of the above list shows that only the first five diamonds - viz. Uncle Sam; Star of Murfreesboro; Lee J. Wagner; Amarillo Starlight and the Star of Arkansas diamonds - were greater than 10 carats in weight, when discovered as rough diamonds. The remaining 24 diamonds were all less than 10 carats in weight when discovered. Hence, we could say that most of the rough diamonds discovered in the park are less than 10 carats in weight.
However, diamond statistics provided by the Crater of Diamonds State Park authorities in their website gives a better picture of the sizes of diamonds discovered in the park. According to this website :-
The total number of diamonds discovered by visitors to the park from 1972 to 2012 = 30,436
Total carat weight of the diamonds discovered = 6,076.48 carats.
Total no of diamonds discovered over 1.00-carat in weight = 900
Therefore total no. of diamonds discovered less than 1.00-carat in weight = 30,436-900 = 29,536
Hence, according to statistics provided by the Park Authorities, majority of the diamonds discovered in the park are less than 1.00-carat in weight.
From 1972 to 2012, a period of 40 years, out of a total of 30,436 diamonds only 900 diamonds were more than 1.00-carat in weight. This works out to a percentage of approximately 3%. Hence, 97% of the diamonds discovered in the Crater of Diamonds State Park are less than 1.00 carat in weight and a substantial number of them in fact fall under the category of "Melee" diamonds, which are less than 0.25 carats (25 points) in weight.

Thanks for your detailed reply. I can now appreciate the reasons behind the decision of the Arkansas State authorities to keep the Crater of Diamonds Park as a diamond hunting area for visitors, where they could prospect for diamonds for a fee and keep what they find. Your detailed reply also provides answers as to why the two diamond prospecting companies, The Arkansas Diamond Mining Company and the Ozark Diamond Mines Corporation, which originally prospected for diamonds in the region, finally wound up their operations, in the early 1950s and formed a partnership in 1952 to develop the site as a tourist attraction, and introduced the novel concept of opening the mine to the public, to prospect for diamonds for a nominal fee and allowing them to keep what they find. The joint-project turned out to be a moderate success, and in 1972, the Arkansas State Government decided to move in, and acquired the park, converting it to the Crater of Diamonds State Park. The new state administration of the park decided to continue with the open policy of allowing the public to scout for diamonds for a fee and keep what they find. Facilities provided for visitors were vastly improved after the State Government took over the administration of the park.

That's one place in US I want to visit when going on a holiday vacation. Who knows, maybe I will be the next to uncover an awesome rough. haha...

Wow