


































Energy and Earth Science 
Vol. 7, No. 1, 2024 

www.scholink.org/ojs/index.php/ees 

ISSN 2578-1359 (Print)   ISSN 2578-1367 (Online) 

 

1 

 

Original Paper 

A Cheap New Geological Dating Method Developed from 

Ancient Shells Study 

Chen Guiqing
1
 & Chen Junhao

1
   

1
 Guangzhou Jinan University 510630, Guangzhou, China 

 

Received: November 25, 2023    Accepted: December 7, 2023   Online Published: March 25, 2024 

doi:10.22158/ees.v7n1p1            URL: http://dx.doi.org/10.22158/ees.v7n1p1 

 

Abstract 

The vast majority of researchers on ancient shells are biologists, who are not familiar with X-ray 

diffractometers, etc. We are physical chemists who use X-ray diffraction to observe the changes in the 

crystal structure of ancient shells? Then use WDX electron probe to observe the changes in the 

microstructure of ancient shells. After discovering shells for a long time, calcite turned into aragonite, 

overturning the conclusion recorded in geological crystallographic books that aragonite’s structure 

and physical properties were unstable and would eventually transform into calcite. Unexpectedly 

discovered that the “Shuang chen Weathering Cave CC” of ancient shells has changed over time, it 

can be used as a new method for geological dating. 

The use of carbon 14 (C14) isotope geological dating method is quite expensive and lacks accuracy, 

causing many jokes. The “Shuang chen Weathering Cave CC” of ancient shells may be used as a new 

geological dating method, and it is quite cheap! 

Keywords 

marine biology, aragonite structure, calcite structure, D/max-1-A type X-ray diffractometer, WDX 

electron probe, CC- double Chen weathering cave 

 

 

 

 

 

 

 

 



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Introduction 

Authoritative textbooks in China: Zhang Xi and Qi Zhongyan’s “Outline of Shellfish Studies” believe 

that the structure of shells can generally be divided into three layers, with the outermost layer called the 

stratum corneum, which is only composed of shell elements. The middle layer is a prism layer, which 

occupies the majority of the shell and is composed of angular columnar calcite (ca1cite). The inner 

layer is usually composed of leaf shaped aragonite, known as the pearl layer, which is glossy, and 

pearls are formed from the nacreous layer. This theory has been widely cited and has been read by 

almost all biology students in China. 

In the 1980s, we used X-ray diffraction to prove that the conclusion that the shell prism layer is a 

calcite structure was completely incorrect, which may have been copied from the Japanese. However, 

shellfish expert Master Hu observed under a microscope and believed that it was still a calcite structure. 

Oh my goodness! In the 1920s, shellfish scientists still don’t know that crystal structure can only be 

determined by X-ray diffraction. The German physicist Roentgen discovered X-rays on November 8, 

1895! 

In the 1980s, Huang Baoyu, a researcher at the Nanjing Institute of Paleontology, provided ancient 

shells: Schistodesmus sp., Schistodesmus lampreyanus (Baird & Adams), Unio douglasiae Griffith 

et Pidgeon, and Lamprotula hazinic (Heude). We use the electron microprobe from the South China 

Sea Institute of Oceanography, Chinese Academy of Sciences! 

Recently, the Corbicula maxima Prime shell was borrowed from Tan Yehui, a researcher at the 

Chinese Academy of Sciences Guangzhou South China Sea Institute of Oceanography, and Dr. Chen 

Zhiyun, and excavated from the Longyan Village Water Conservancy Project in Shunde, Guangdong. 

Collectors: Zhao Huanting et al. Collection time: February 1961. Era: 500 to 1000 years ago. 

Measurement date/time: 2015-11-27 9:48:41. Using the Empyrean X-ray diffractometer from Sun Yat 

Sen University. 

 

 

 

 

 

 

 

 

 

 

 

 



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The first part  

Comparison of X-ray diffraction lines between modern and ancient shells 

Grind each layer of the shell into powder using an agate mortar and pass it through a 360 mesh sieve. 

Using D/max-1-A X-ray diffractometer and Cu target KαX-ray diffraction, under 40kV, 50mA 

conditions, within 30 minutes from 2θ Range 20
0
-80

0
, instrument uses a Plot plotter and automatically 

prints 2θ, Absolute strength I and corresponding crystal plane group spacing d. Refer the above results 

to the international universal phase analysis (JCPDS) card to determine the crystal structure of the 

sample. 

d=0.3399nm, and the horizontal bars at the bottom of the spectral lines are all aragonite structured 

spectral lines. 

1. X-ray Diffraction Results 

 

Table 1. X-ray Diffraction Data of Modern and Ancient Shells 

Modern Cristaria  

plicata(Leach) Shell Powder 

Corbicula maxima 

pearl layer 

Corbicula maxima 

prismatic layer 

Corbicula maxima 

periostracum layer 

d( nm) I/I0 % d (nm) I/I0 % d(nm) I/I0 % d( nm) I/I0 % 

0.3399 99.99 0.2875 100.00 0.3407 5.31 0.3399 90.81 

0.3276 51.05 0.2706 58.06 0.3287 2.61 0.3279 54.75 

0.2875 11.22 0.1862 1.48 0.2879 10.97 0.2703 54.46 

0.2705 79.03 0.1744 2.09 0.2709 100.00 0.2484 46.31 

0.2487 41.80 0.1438 5.77 0.2492 16.96 0.2413 20.54 

0.2412 16.49 0.1415 32.81 0.2378 27.43 0.2377 56.42 

0.2376 53.68 0.1361 3.21 0.2334 13.13 0.2345 36.76 

0.2342 37.09   0.1979 1.33 0.2193 16.07 

0.2333 33.62   0.1881 1.45 0.2110 28.15 

0.2192 14.26   0.1817 2.48 0.1980 100.00 

0.2108 31.65   0.1747 42.95 0.1883 50.92 

0.1980 100.00   0.1729 21.7 0.1819 41.6 

0.1883 47.76     0.1746 46.3 

0.1817 37.27       

0.1761 5.95       

0.1745 50.73       

0.1728 30.45       

 



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Position [°2Theta] (Copper (Cu))

10 20 30 40 50 60 70

Counts

0

1000

2000

3000

4000

 SCSMBC007426 NC

Position [°2Theta] (Copper (Cu))

10 20 30 40 50 60 70

Counts

0

1000

2000

3000

 SCSMBC007426 ZC

Position [°2Theta] (Copper (Cu))

10 20 30 40 50 60 70

Counts

0

200

400

600

800

 SCSMBC007426 WC

 

X-ray diffraction pattern: Figure 1 Modern Cristaria plicata (Leach) Shell Powder. Figure 2 Corbicula 

maxima pearl layer. 

Figure 3 Corbicula maxima prismatic layer. Figure 4 Corbicula maxima periostracum layer.  

 

2. Discussion of Results 

2.1 

The crystal structure of ancient shells is the same as that of modern shells. The prismatic layer is all 

aragonite structure, which overturns the conclusion of “shellfish outline”. 

2.2  

The X-ray diffraction pattern of the pearl layer in the Corbicula maxim shell appears very special, with 

the absolute intensity of the strongest spectral line d=0.2875nm reaching I=4290.7 (the maximum 

intensity of the spectral line in a typical shell is about 700). The spectral lines are very strong, narrow, 

and few, all of which are thick aragonite grains with obvious “monocrystallization” and no impurity 

spectral lines. Unlike geological crystallography think, where the structure of aragonite is unstable, it 

will eventually become calcite. But rather development towards a higher degree of single crystal 

indicates that the structure of aragonite is stable. 

According to the Scherrer formula of X-ray diffraction theory of crystals, the strengthening, narrowing, 

and decreasing of spectral lines are caused by the growth and thickening of grains in this diffraction 

direction (preferential orientation growth), which we refer to as the “single crystal tendency”. 

The growth process of seashells is the growth process of aragonite crystals, constantly in an unbalanced 

state. Due to vacancies or impurities filling the lattice, the lattice distortion changes the spacing 

between crystal planes and broadens the spectral lines, resulting in new internal stresses. After the 

death of shellfish, crystal growth stops and no new internal stress is generated. The stress inside the 

shell gradually releases, vacancies are gradually filled or impurities are gradually eliminated to the 



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grain boundary to eliminate internal stress. At this time, internal stress is also concentrated at the grain 

boundary, so this area is prone to weathering. The grains of aragonite continue to grow, therefore; 

Make the spectral lines stronger, narrower, and fewer! 

Due to the Corbicula maxima shell, it is less affected by the surrounding soil, which better reflects this 

process. 

2.3  

The X-ray diffraction pattern of the prismatic layer of the Corbicula maxim shell is similar to that of 

the pearl layer, with strong, narrow, and few spectral lines. All spectral lines are thick aragonite grains 

with a “single crystal tendency”, and there are no impurity spectral lines. 

The absolute intensity of the strongest spectral line d=0.2709nm reaches I=3406.33, which is very 

strong, narrow, and has very few spectral lines! But because the prism layer is located in the middle of 

the shell, between the nacre layer and the stratum corneum, the internal stress release is slower, so the 

spectral lines are slightly more than the nacre layer. It is exactly the same as the pearl layer. From its 

X-ray diffraction pattern, it appears that many weak spectral lines have become almost flattened and 

are developing towards a “monocrystalline trend”, similar to the pearl layer above, without impurity 

spectral lines. 

2.4  

X-ray diffraction pattern of periostracum layer of the Corbicula maxim shell. Due to the influence of 

the epidermis, the spectral lines become more numerous and wider. But all spectral lines are of 

aragonite structure and have no impurity spectral lines. 

2.5  

It can be seen from the table that there are more spectral lines in the shell of modern pleated clamshell 

than that of ancient clam shell. Especially from the spectrum diagram is clear at a glance. The aragonite 

structure of the ancient shell continues to grow, with obvious “monocrystalline”, excluding impurities. 

Modern shells contain some calcite, but ancient shells contain almost no calcite. It shows that after a 

long age of shells, calcite becomes aragonite! 

 

 

 

 

 

 

 

 

 

 



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The second part  

Electron Microprobe experiment of four kinds of ancient shells 

1. Materials and Methods 

In the 1980s, researcher Huang Baoyu from the Nanjing Institute of Paleontology provided us with four 

types of ancient shells and explored them using the Electron Microprobe from the South China Sea 

Institute of Oceanography, Chinese Academy of Sciences! 

 

2. Experimental Results 

2.1  

Schistodesmus sp.shell. 102 points, Ding Village, Xiangfen, Shanxi, with field number ADY201 

1983/9/9. Era: hundreds to thousands of years. 

Elements with atomic numbers below 11 (Na) cannot be measured, therefore; CaCO3 can only be 

calculated from the CaO molecular formula. The results are shown in Table 1. 

CaO+CO2--→CaCO3      MCaCO3=(100.089÷56.0794)×MCaO=1.784777×M CaO. 

56.0794      100.0892 

Inner layer MCaCO3=1.78478×48.165=85.964; Surface MCaCO3=1.78478×45.125=80.538. The same 

applies below. 

Total in the table Ʃ The sum of calcium carbonate and other oxides. Sum of electron probe 

measurements of modern shells Ʃ. They are all around 100%, which is caused by errors caused by 

certain factors and can be normalized to 100%. However, the results of ancient shells are at a certain 

distance from 100%. This is the result of ancient shells weathering for thousands of years, and we 

define it as the “Shuang Chen Weathering Cave”: CC=100-Ʃ. The various parts of ancient shells are 

different, and the average value CC
-------

 is taken to represent them. According to the dozens of modern 

shells we tested, the general result is 98.5<Ʃ. Therefore, it is assumed that CC values below 2 can be 

ignored and considered as 0, indicating that there is no “Shuang Chen Weathering Cave”. Because 

the range of electron probe testing is very small, important data needs to be measured at several points 

to obtain the average value, the same below.  

2.2  

Schistodesmus lampreyanus (Baird & Adams) shell 102 points, Ding Village, Xiangfen, Shanxi, 

1986/12/16. Era: hundreds to thousands of years. The results are shown in Table 2. 

2.3  

Unio douglasiae Griffith et Pidgeon shell. No.102, Dingcun, Xiangfen, Shanxi, with field number 

ADY201 1986/12/16. Era: hundreds to thousands of years. The results are shown in Table 3. 

 

 

 



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2.4 

Lamprotula hazinic (Heude) shell. 102 points in Ding Village, Xiangfen, Shanxi, with field number 

ADY193 1986/12/16. Era: hundreds to thousands of years. The results are shown in Table 4. 

2.5  

Modern Pinctada Martensi (Dunker) pearl shell. The results are shown in Table 5. 

2.6 

Modern Lamprotula mansuyi (Dautzenberg et Fischer) shell. The results are shown in Table 6. 

2.7 

Modern Mactra Antiquata Spengler shell. The results are shown in Table 7. 

2.8  

Modern Arca (Anadara) granosa Linnaeus shell. The results are shown in Table 8. 

 

Table 1-8. Oxide of Shell 

Oxide Na2O K2O Fe2O3 MnO SiO2 MgO TiO2 Al2O3 CaO 
CaCO

3 
Ʃ CC CC

-------

 

Table 1 Ancient Schistodesmus sp. 
Inner layer 0.254 0.000 0.000 0.028 0.058 0.040 0.045 0.066 48.165 85.964 86.455 13.54 15.9 
Table 2 Ancient Schistodesmus lampreyanus 
Inner layer 0.151 0.005 0.000 0.000 0.044 0.034 0.000 0.040 43.156 77.024 77.298 22.70 

19.9 
Surface layer 0.168 0.008 0.046 0.028 0.103 1.227 0.000 0.046 45.512 81.229 82.855 17.14 
Surface layer 0.188 0.024 0.092 0.000 0.571 0.146 0.022 0.142 45.125 80.538 81.723 18.28  
Table 3 Ancient Unio douglasiae 
Inner layer 0.113 0.026 0.031 0.042 0.029 0.046 0.000 0.061 45.758 81.668 82.016 17.98 

19.3 
Surface layer 0.104 0.000 0.015 0.028 0.073 0.012 0.000 0.030 44.361 79.175 79.437 20.56 
Table 4 Ancient Lamprotula sp. 
Inner layer 0.254 0.000 0.092 0.042 0.029 0.000 0.046 46.730 83.403 83.901 83.901 16.10 

12.8 
Surface layer 0.217 0.005 0.230 0.000 0.059 0.000 0.086 50.298 89.771 90.415 90.415 9.58 
Table 5 Modern Pinctada fucata martensi 

Pearl layer 0.516 0.007 0.020 0.018 0.038 0.058 0 0.030 55.644 99.313 
100.00
0 

0 

0 Prismatic layer 0.429 0.023 0.039 0.000 0.000 0.085 0 0.065 55.670 99.360 
100.00
0 

0 

Periostracum 0.282 0.039 0.000 0.000 0.019 1.205 0 0.048 55.137 98.409 
100.00
0 

0 

Table 6 Modern Lamprotula mansuyi 

Pearl layer 0.38 0.03 0.08 0.07 0.37 0.06 0 0.11 55.65 99.323 
100.42
3 

0 

0 
Prismatic layer 0.59 0.09 0.06 0.11 0.43 0.05 0 0.12 55.67 99.359 

100.80
9 

0 

Periostracum 0.25 0.00 0.00 0.04 0.42 0.03 0 0.08 55.38 98.841 99.661 0 
Table 7 Modern Coelomactra antiquate 
A region 0.62 0.02 0.03 0.00 0.02 0.04 0 0.05 55.59 99.216 99.996 0 

0 
B region 0.60 0.03 0.00 0.02 0.03 0.00 0 0.00 55.65 99.323 

100.00
3 

0 

Table 8 Modern Tegillarca granosa 
A region 0.56 0.01 0.00 0.04 0.03 0.07 0 0.03 55.61 99.252 99.992 0 

0 
B region 0.53 0.01 0.00 0.00 0.00 0.07 0 0.03 55.67 99.360 

100.00
0 

0 

 

 

 



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Table 9. Comparison of the “Double Chen Weathered Hole CC” Result between Ancient and 

Modern Shells 

Ancient shell species 
Oxide 
summation 
Ʃ
—

 

Double Chen 
weathered hole 
CC
-------

 
Moder shell species 

Oxide 
summation 
Ʃ
—

 

Double Chen 
weathered hole CC

-------

 

Schistodesmus sp. 84.09 15.9 Pinctada martensi shell 100.00 0 
Schistodesmus 
lampreyanus 

80.08 19.9 
Lamprotula mansuy 
shell 

100.30 0 

Unio douglasiae 80.73 19.3 Mactra antiquate shell 100.00 0 

Lamprotula sp. 87.16 12.8 
Arca (Anadara) granosa 
shell 

100.00 0 

 

3. Result Discussion 

3.1 

We studied the electron probe Electron Microprobe detection of 8 samples from 4 ancient and 4 

modern shells. As a result, many voids were found in the ancient shell-“Shuang chen Weathering Cave 

CC” as shown in Table 9! We hope it can become a cheap method for dating ancient artifacts! 

3.2 

In order to achieve the purpose of this article, we sincerely hope that relevant researchers can conduct 

further research! 

 

Funding  

90 year old commemorative works IV 

Fund project “Artificial growth of aragonite crystals and artificial development of pearls” 

Chen Guiqing, Chen Junhao 1985 (Approval No. 85084). 

Fund project “Research on the Structure and Imaging Mechanism of Artificial Pearl Cores and Artistic 

Pearl Images”  

Chen Guiqing, Chen Junhao. 1989 (Approval number 38870643). 

 

References 

Cao, B. X. (2014). AMS carbon C14 dating method and analysis. Baidu Wenku-Education-Higher 

Education-Science. 

Chen, G. Q., & Chen, J. H. (1988). A study on the crystal structure types of seashells. Chinese Marine 

Medicine, 1988(1-2), 21-29. https://doi.org/10.2753/CED1061-1932210129 

Chen, G. Q., & Chen, J. H. (2017). New Conclusion on the Crystal Structure of Pearls and Shells. 

Journal of Applied Oceanography, 36(4). 

Chen, G. Q., Chen, J. H., & Chen, P. (1987). A study on the natural pearls and shells of Pinctada 

martensii. Marine Medicine, 1986(3), 4-7.  

 

 

https://doi.org/10.2753/CED1061-1932210129


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Chen, G. Q., Chen, J. H., & Chen, S. Y. (1996). Study on the structural components and heating 

treatment of calcium carbonate medicinal materials (Volume 1, Volume 2, p. 1670). Science and 

Technology Literature Press. 

Chen, J. H., & Chen, G. Q. (2018). Exploration of Crystal Structure and Application of Pearls and 

Shellfish. Jinan University Press. 

Chen, J. H., & Chen, G. Q. (2019). The Ancient Shells Are Deduced by X-ray Diffraction and Electron 

probes. Journal of Water Resources and Ocean Science, 8(6), 86. 

https://doi.org/10.11648/j.wros.20190806.11 

Editorial group of “Manual of Mineral X-ray Powder Identification”. (1978). Guiyang Institute of 

Geochemistry, Chinese Academy of Sciences. 

Kaiichi, M. (1965). Zhenzhu Chronicle, Beilongguan. 

Kobayashi, S., & Watanabe, T. (1961). Research on pearls 169-176. Technical Hall. 

Method for determining geological age. (n.d.). 360 library. 

Rock and Mineral Research Office, Department of Geology, Nanjing University. (1978). 

Crystallography and Mineralogy. Beijing: Geological Publishing House. 

Ruo, S. (edited and proofread). (n.d.). Carbon C14 dating and Chinese prehistoric archaeology. 

Zhang, X., & Qi, Z. Y. (1961). Outline of Shellfish Science. Science Press. 

Zhao, S. R. (Ed.). Crystallography and Mineralogy (p. 412). Geological Publishing House. Curriculum 

textbooks for higher education in the 21st century. 

 

https://doi.org/10.11648/j.wros.20190806.11

