


































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

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

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

 

10 

 

Original Paper 

Textbook Error Theory about Aragonite Structure 

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.v7n1p10           URL: http://dx.doi.org/10.22158/ees.v7n1p10 

 

Abstract 

Science constantly discovers new theories and concepts, overturning erroneous theories and concepts. 

Textbooks never correct, fallacies are left to future generations. There are two erroneous theories 

about the structure of aragonite in textbooks: (1) The authoritative Chinese textbook “Outline of 

Shellfish Studies” by Zhang Xi and Qi Zhongyan believes that shells can be divided into three different 

crystal structures, with the middle layer being a prismatic layer that occupies the majority of the shell 

and is composed of calcite (cubic crystal system, hexagonal crystal cells). The shellfish academic 

community in China quotes many Japanese literature, and these theories may have been copied from 

Japan. (2) The geological crystallography book records that the structural physical properties of 

aragonite are unstable and will eventually transform into calcite. We use X-ray derivatives found that 

after a long geological time, aragonite not only did not become calcite, but also the grain is growing 

large: monocrystalline, calcite is still decreasing, calcite is changing to aragonite. 

Keywords 

marine biology, X-ray diffraction, Shell, Prismatic pearls, Aragonite structure, Calcite structure, 

Geology and crystallography 

 

1. Introduction 

Recently, we consulted renowned shellfish scientist Xie Yukan from the South China Sea Institute of 

Oceanography, Chinese Academy of Sciences to discuss this issue. It is understood that his graduate 

students still believe that the prismatic layer of the shell is composed of calcite through microscopic 

verification. Do shellfish scientists still not know that crystal structure can only be determined by X-ray 

diffraction, or by observing morphology under a microscope? The German physicist Roentgen 

discovered X-rays on November 8, 1895! In 1959, Shinjiro Kobayashi and Tetsuko Watanabe from 

Japan proposed that prismatic pearls have a calcite structure. Many domestic and foreign papers have 

not raised objections to this, which is wrong. Japanese shellfish scientists are also unfamiliar with 



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crystallography. 

What changes will occur when shells are buried in the ground for thousands of years? The geological 

crystallography book records that the physical properties of aragonite structure are unstable and will 

eventually transform into calcite, which has become common knowledge. Wrong, it's the 

transformation of calcite into aragonite structure. 

Aragonite gemstones are composed of minerals such as aragonite, calcite, iron oxide, and opal, and 

belong to secondary minerals with aragonite as the main component. Only Xizang, Penghu in Taiwan 

Province and Sicily in Italy produce aragonite gemstones in the world. In theory, there should not be 

any aragonite gemstones in the world, because after billions of years, all the aragonite structures it 

contains have already transformed into calcite structures. However, in reality, they still exist, indicating 

that this theory is incorrect. 

 

2. Materials and Methods 

2.1 Modern Shells 

The following shells are provided by Xie Yukan, Sanya Director of the South China Sea Institute of 

Oceanology, CAS. 

Pinctada martensi, Pinctada maxima, Hyriopsis cumingii, Cristaria plicata, Pteria (Magnavicula) 

penguin, Pinctada margaritifera, Pinctada nigra, Pinctada chemnitzi, Anodonta woodiana, Lamprotula 

mansuyi, Mactra antiquate, Arca (Anadara) granosa, Meretrix meretrix, Perna viridis, Tridacna 

(Chamestrachea) squamosa, (Meretrix meretrix), Nautilus pompilius, Trochous nilotticus, Turbo 

chrysostomus, Erosaria caputserentis, Trachycadium flavum, Macoma truncate, Corbicula fluminca，

Haliotis diversicolor, Nerita albicilla, Mytilus edulis, Spondylus nicobaricus, Chama dunker and Abra 

profundorum. 

The pearl and shell is ground into powder with agate mortar and passed through a 360-mesh screen. 

Using the D/max-1-A type X-ray diffractometer, using the Cu target Kα ray diffraction, under the 

conditions of 40kV and 50mA, within 30min from 2θ range 20
0
-80

0
, the instrument uses the Plot 

plotter, automatically prints 2θ, the absolute intensity I and the corresponding crystal face group 

spacing d. Refer the above results to the international universal phase analysis (JCPDS) card to 

determine the crystal structure of the sample. 

d=0.1974nm, and the bottom crossbar of the spectral line has an aragonite structure. d=0.3030nm, and 

the dashed line at the bottom of the spectral line shows a calcite structure. d=0.3019, the calcite III 

structure with ripple at the bottom of the spectral line, and the silica structure with rod, point, and rod at 

the bottom of the spectral line with d=0.3336. 

 

 

 



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2.2 Ancient Shells 

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

of ancient seashells, such as splitodonta, splitodonta radiata, Euhylidia Dui and Liunia, which were 

collected from 102 points in Ding Village, Xiangfen, Shanxi Province, and were all hundreds to 

thousands of years old. 

Borrowed four ancient shells from Dr. Tan Yehui and Dr. Chen Zhiyun of the South China Sea 

Institute of Oceanography in Guangzhou: the Clams marmosa, the smooth blue clams, the river clams 

and the great clams. The first three species were collected from the late Quaternary loose sedimentary 

rock center of Yuanzhou Production Team 1 well, Shunde, Guangdong Province. In the early 1970s. 

The fourth kind was extracted from Longan village water conservancy project in Shunde, Guangdong 

Province. Years 500 to 1,000 years. 

Grind as above into powder and pass through 360 mesh screen. It was diffracted by Empyrean X-ray 

diffractometer. 

 

3. Experimental Results 

3.1 Pearl Layer Structure of Shells 

Only the pearl layer of the Ostrea rivularis shell has a calcite structure. The white inner layer of the 

Pinna atropururea shell is also a aragonite structure, and the black luminescent part around it is a 

calcite structure, which is also considered a pearl layer. 

The pearl layer of the other shells is entirely composed of aragonite structure. Explain that the above 

theory is correct. 

3.2 Prismatic Layer Structure of Shells 

At present, only the prismatic layer of the Pinna atropura shell is found to be a ca1cite structure, while 

the loose part of the Ostrea rivularis shell is a calcite ca1cite-III structure. The prism layers of the other 

shells are all aragonite structures. This indicates that the above theory is incorrect. 

Some shells are too thin to be layered, so they have to undergo full shell X-ray diffraction. The 

majority of the entire shell of Spondylus nicobaricus, Haliotis diversicolor, Nerita albicilla, Mytilus 

edulis, Chama dunker, and Abra profundorum are also aragonite structures. 

3.3 The Periostracum Layer Structure of Shells 

Contains a large amount of amorphous organic matter. Some shells also contain aragonite structures. 

Some shells also contain calcite structure ca1cite. The “Outline of Shellfish Science” states that it is 

incorrect for the stratum corneum of shells to be composed solely of “conchiolin”. 

3.4 Prismatic Pearls Are All of Aragonite Structure, Without Calcite Structure 

3.5 Schistodesmus Sp. Prismatic Layer  

Wilderness number ADY201, 1983/9/9. All spectral lines are aragonite structure, no impurity spectral 

lines. 



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3.6 Schistodesmus Lampreyanus (Baird & Adams) Prismatic Layer 

Wilderness number ADY201, 1986/12/16. All spectral lines are aragonite structure, no impurity 

spectral lines. 

3.7 Unio Douglasiae Griffith et Pidgeon 

Wilderness number ADY201,1986/12/16. 

3.7.1 Unio Douglasiae Pearl Layer 

The only weak spectral line of calcite appears, with a relative aragonite content of 0.15% in calcite. All 

other spectral lines are aragonite structured. 

3.7.2 Unio Douglasiae Periostracum Layer  

All spectral lines are aragonite structure. 

3.8 Lamprotula Hazinic (Heude) Shell 

Wilderness number ADY193, 1986/12/16. 

3.8.1 Lamprotula Hazinic Pearl Layer 

All spectral lines are aragonite structure, no impurity spectral lines. 

3.8.2 Lamprotula Hazinic Prismatic Layer 

The only weak spectral line of calcite is d104=0.3034nm. The relative content of calcite is 0.23%. All 

other spectral lines are of aragonite structure. 

3.8.3 Lamprotula Hazinic Periostracum Layer 

The only weak spectral line of calcite is d104=0.3024nm. The relative aragonite content is 0.17%. All 

other pectral lines are aragonite. 

3.8.4 Pearl Cores Made from Modern Lamprotula Hazinic Shells 

All spectral lines are aragonite structure. 

3.9 Trapezidae, Trapezium Liratum (Reeve, 1843) Periostracum Layer 

The results are shown in Table 1, the same below. Two strong silica spectral lines appeared with 

d=0.3370nm and I/I0=70.2%; d=0.1824nm, I/I0=56.00%, which is the silica that ancient shells have 

adhered to in soil for many years, because modern shells have never seen these spectral lines; All other 

spectral lines are of aragonite structure.  

3.10 Corbulidae, Potamacorbula Laevis (Hinas) Periostracum Layer 

All spectral lines comply with card 041-1475, All pectral lines are aragonite structure, no impurity 

spectral lines. 

3.11 Corbiculidae, Corbicula Fluminea (Müller) 

3.11.1 Corbicula Fluminea Prismatic Layer 

All spectral lines are aragonite structure, no impurity spectral lines. 

3.11.2 Corbicula Fluminea Periostracum Layer 

The majority of the spectral lines below the second strongest in the table are aragonite structures. 

Two weak calcite spectral lines appeared: d104=0.3033nm, I/I0=8.71%, and d113=0.2282nm, I/I0=7.26%. 



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The strongest spectral line of aragonite is d=2697nm, and I/I0=67.1%. The strongest spectral line of 

calcite is d=0.3033nm, and I/I0=8.71%. The relative aragonite content of calcite is 1.2%. 

The strongest spectral line d=0.3336nm is the strongest spectral line of silica SiO2, and the spectral line 

d=0.4249nm is the second strongest spectral line d100=0.4255nm of silica SiO2. 

There is also a spectrum line d=0.3205 nm and I/I0=18.38%, which is unknown. 

The stratum corneum of river clams contains a high amount of silica, which has been stuck in the soil 

for many years, because modern shells have never seen these spectral lines. If it is removed, it still has 

a relatively complete aragonite structure, and the aragonite spectral lines of ancient river clam shells are 

the same as those of modern river clam shells, without any changes. 

3.11.3 Modern Corbicula Fluminea Prismatic Layer 

The only weak impurity mass spectrum line appeared, d=0.3632nm, I/I0=3.21%, and All other spectral 

lines are of aragonite structure. 

3.12 Corbiculidae, Corbicula Maxima Prismatic Layer 

Excavated from the Longyan Village Water Conservancy Project in Shunde, Guangdong. Collection 

time: February 1961. 

3.12.1 Corbicula Pearl Layer 

The X-ray diffraction pattern is 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 a 

strong “single crystal tendency” and no impurities. Unlike geological crystallography, where the 

structure of aragonite is unstable, it will eventually become calcite. Instead, it develops towards a 

higher degree of crystallization, indicating 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 the shell pearl layer is the process of aragonite crystal growth, constantly in an 

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

crystal plane group spacing d, causing the spectral lines to widen and continuously generating 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 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 large size of the clam shell, it is less affected by the surrounding soil, which better reflects 

this process. 

 



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3.12.2 Corbicula Prismatic Layer 

It X-ray diffraction pattern of the prismatic layer of the clam 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 prism layer is between the nacre and the stratum corneum, and the internal stress release is slower, 

so the spectral lines are slightly more than the nacre. 

3.13.3 Corbicula Periostracum Layer 

All spectral lines are aragonite structure, no impurity spectral lines. 

According to the X-ray diffraction diagram of the corneum of large corbicula shell on the right of 

FIG.1, the absolute intensity of the strongest spectral line d=0.1980nm I=481.16. Due to the large 

amount of amorphous organic matter in the corneum, the monocrystallization is affected, which greatly 

reduces the absolute intensity and slightly increases the spectral line. Once again proved the ancient 

shell monocrystalline trend! 

 

Table 1. X-Ray Diffraction Data Various Shells  

Pinctada 

martensi pearl 

layer 

Pinctada 

martensi  

prismatic layer 

Pinctada 

martensi 

periostracum 

Pinctada maxima 

pearl layer 

Pinctada maxima 

prismatic layer 

Pinctada 

maxima 

periostracum  

Perna viridis  

pearl layer 

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

(%) 

d (nm) I/I0 (%) d 

(nm) 

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

(%) 

0.3387 100 0.3394 79.2 0.3020 100 0.3397 100 0.3391 55.8 0.303

1 

100 0.339

0 
69.88 

0.3264 48.8 0.3270 44.3 0.2483 12.6 0.3272 47.3 0.3266 30.3 0.248

8 

12.1 0.326

8 
37.01 

0.3018 5.76 0.3026 13.5 0.2274 13.8 0.2702 65.7 0.2697 100 0.227

9 

14.5 0.269

7 
100 

0.2695 77.4 0.2699 100 0.2084 13.7 0.2483 39.2 0.2481 32.8 0.208

9 

11.8 0.248

1 
38.47 

0.2368 51.6 0.2371 47.2 0.1904 13.8 0.2373 46.4 0.2369 43.8 0.190

9 

15.4 0.236

9 
44.8 

0.1972 46.3 0.1975 38,9 0.1867 13,7 0.1976 51.7 0.1973 27.3 0.187

1 

12.9 0.197

3 
34.58 

 

 

 

 



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Table 2. Continued Table 1 

Perna viridis  

prismatic layer 

Perna viridis  

periostracum  

Pinna 

atropurpurea 

pearl layer 

Pinna 

atropurpurea 

prismatic layer 

Pinna atropurpurea 

periostracum  

Hyriopsis cumingii  

Full shell 

Cristaria plicata 

Inner middle 

layer 

d (nm) I/I0 (%) d 

(nm) 

I/I0 

(%) 

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

0.3392 
100 

0.340

1 
100 

0.3402 
58.81 

0.3854 
12.33 

0.3028 
100 

0.3401 61.1 0.3400 65.4 

0.3269 
58.06 

0.327

6 
66.98 

0.2876 
39.16 

0.3034 
100 

0.2486 
13.78 

0.3277 34. 1 0.2874 39.6 

0.2699 
70.44 

0.270

5 
55.07 

0.2706 
100 

0.2282 
17.01 

0.2277 
14.59 

0.2704 100 0.2703 100 

0.2370 
52.06 

0.248

6 
43.17 

0.2487 
41.81 

0.2091 
14.37 

0.2087 
13.67 

0.2374 36,3 0.2484 38.6 

0.1975 
50.07 

0.197

8 
60.89 

0.2375 
36.58 

0.1910 
19.1 

0.1908 
21.35 

0,1977 37.2 0.2373 40.3 

0.1877 
36.22 

0.188

0 
42.76 

0.1978 
37.13 

0.1873 
16.45 

0.1870 
16.51 

0.1743 35,2 0,1977 40,6 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



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Table 3. Continued Table 2 

Cristaria  

plicata 

periostracum  

Ostrea rivularis 

inner layer 

Ostrea 

rivularis 

Loose part 

Ostrea rivularis 

Lower shell 

surface 

Ostrea rivularis 

Upper shell 

surface 

Prismatic pearl 

powder 

Prismatic pearl 

inner surface 

layer 

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

(%) 

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

(nm) 

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

(%) 

0.3421 100 0.3032 100 0.3831 8.9 0.3032 100 0.303

1 
100 

0.340

2 

95.03 0.2755 20.33 

0.3295 54.3 0.2491 5.5 0.3019 100 0.2491 11.2 0.249

0 
10.3 

0.327

8 

50.40 0.2716 100 

0.2716 83.3 0.2281 10.1 0.2274 14.8 0.2281 16.8 0.228

0 
15 

0.270

8 

100.00 0.2499 19.89 

0.2495 43.1 0.2091 6.9 0.2085 11.4 0.2091 12.3 0.209

0 
13 

0.248

6 

35.94 0.2383 19.36 

0..238

3 

42.8 0.1909 24.4 0.1904 17.7 0.1909 20.0 0.190

9 
20.7 

0.237

8 

40.89 0.1822 16.97 

0.1983 77.7 0.1873 14.3 0.1868 17.4 0.1872 17.6 0.187

2 
17.4 

0.2335 
22.42 

0.1751 41.15 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



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Table 4. Shell X-ray Diffraction Data 

Schistodesmus 

sp. 

 prismatic 

layer 

Schistodesmus 

lampreyanus 

prismatic layer 

Unio 

douglasiae 

 pearl layer 

Unio douglasiae 

Periostracum  

layer 

Lamprotula 

sp. pearl 

layer 

Lamprotula 

sp. 

prismatic 

layer 

Lamprotula sp. 

Periostracum 

layer 

Modern 

Lamprotula 

sp.Pearl nuclei 

d nm I/I0% d nm I/I0% d nm I/I0% d nm I/I0% d nm I/I0% d nm I/I0% d nm I/I0% d nm I/I0% 

0.3400 
91.4 

0.3398 
73.2 

0.3399 
66.6 

0.3397 
100 

0.3399 
58.9 

0.340

1 
100 

0.3397 
100 

0.3395 
53.9 

0.3275 
48.4 

0.3274 
43.6 

0.3275 
35 

0.3274 
51.6 

0.3274 
31.3 

0.327

7 
51 

0.3274 
51 

0.3273 
31.9 

0.2702 
100 

0.2702 
100 

0.3038 
1.64 

0.2700 
63.2 

0.2702 
100 

0.303

4 
2.6 

0.3024 
1.9 

0.2700 
100 

0.2484 
52.9 

0.2484 
42.9 

0.2702 
100 

0.2483 
38.3 

0.2484 
37.3 

0.270

3 
61 

0.2482 
31.4 

0.2483 
32.9 

0.2373 
55.4 

0.2373 
46.9 

0.2484 
40.4 

0.2371 
37.6 

0.2373 
40.3 

0.237

3 
39.8 

0.2338 
35 

0.2371 
31.6 

0.1977 
52.9 

0.1976 
39.5 

0.2373 
41.2 

0.1976 
61 

0.1976 
29.4 

0.197

7 
64.8 

0.1976 
76.3 

0.1976 
31.9 

 

Table 5. Continue Table 4 

Trapezium 

liratum 

periostracum 

layer 

Potamacor 

bula laevis 

periostracum 

layer 

Corbicula 

fluminea 

prismatic 

layer 

Corbicula 

fluminea 

periostracum 

layer 

Modern 

Corbicula 

fluminea 

prismatic 

layer 

Corbicula 

maxima 

pearl layer 

Corbicula 

maxima 

prismatic 

layer 

Corbicula 

maxima 

periostracum 

layer 

d nm I/I0% dnm I/I0 % d nm I/I0 % d nm I/I0 % d nm I/I0 % d nm I/I0 % d nm I/I0 % d nm I/I0 % 

0.3418 100.00 0.2885 23.50 0.3404 31.86 0.4249 17.42 0.3632 3.21 0.2875 100.0 0.2879 10.97 0.3399 90.81 

0.3370 70.20 0.2725 76.00 0.3282 15.23 0.3336 100.0 0.3409 100.0 0.2706 58.06 0.2709 100.00 0.3279 54.75 

0.2121 13.89 0.2705 100.00 0.2706 100.0 0.3033 8.71 0.3285 50.6 0.1744 2.09 0.2492 16.96 0.2703 54.46 

0.1989 78.70 0.2488 49.58 0.2491 31.42 0.2697 67.10 0.2709 94 0.1438 5.77 0.2378 27.43 0.2377 56.42 

0.1890 59.93 0.2375 54.28 0.2377 51.42 0.2485 30.65 0.2377 53.6 0.1415 32.81 0.2334 13.13 0.1980 100.0 

0.1824 56.00 0.2332 25.17 0.2332 22.73 0.2282 7.26 0.1980 52.4 0.1361 3.21 0.1747 42.95 0.1883 50.92 

 

 

 

 

 

 



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Table 6. Relative Aragonite Content of Calcite in Ancient and Modern Shells 

 

 

The content of calcite relative aragonite in ancient shells is less than 2%, which is negligible 

Schistodesmus sp.  

Shell prismatic layer 

0% Lamprotula hazinic 

Shell prismatic layer 

0.23% Corbicula fluminea  

shell periostracum layer 

0.78% 

Schistodesmus 

lampreyanus 

 shell prismatic layer 

0% Lamprotula hazinic   

Shell prismatic layer 

0.17% Corbicula maxima  

shell pearl layer 

0% 

Unio douglasiae  

shell pearl layer 

0.15% Trapezium liratum  

shell periostracum layer 

0% Corbicula maxima  

shell mprismatic layer 

0% 

Unio douglasiae  

shell periostracum layer 

0% Potamacor bula laevis  

shell periostracum layer 

0% Corbicula maxima  

shell periostracum layer 

0% 

Lamprotula hazinic  

shell pearl layer 

0% Corbicula fluminea  

shell prismatic layer 

0%   

Calcite relative aragonite content in modern shells 

Pinctada martensi  

shell periostracum layer 

100% 

calcite 

Pinctada chemnitzi 

shelll periostracum layer 

100% 

calcite 

Haliotis diversicolor shell 8.3% 

Pinctada maxima  

shell periostracum layer 

100% 

calcite 

Ostrea rivularis Gould shell 

 Most of the majority 

100% 

calcite 

Nerita albicilla shell 14% 

Pteria (Magnavicula) 

Penguin 

shell periostracum layer 

100% 

calcite 

Pinna atropurpurea Sowerby 

Shell prismatic layer 

100% 

calcite 

Mytilus edulis shell  22% 

Pinctada margaritifera 

shell periostracum layer 

100% 

calcite 

Pinna atropurpurea Sowerby 

shell periostracum layer 

100%c

alcite 

Chama dunker shell  15% 

Pinctada nigra 

Shell periostracum layer 

100% 

calcite 

Spondylus nicobaricus shell 8.5% Abra profundorum shell  

 

19% 



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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

 

Corbicula maxima X-ray diffraction pattern: Figure 1. Pearl Layer. Figure 2. Prismatic Layer. 

Figure 3. Periostracum Layer 

 

3. Research Conclusion 

3.1  

The “Outline of Conchology” believes that it is correct that the nacreous layer of the shell is aragonite 

structure, but the peral layer of the oyster shell and the black shiny nacreous layer of the purple cracker 

are calcite structure. 

3.2  

The “Outline of Conchology” believes that it is wrong that the prismatic layer of shell is calcite 

structure. At present, only the prismatic layer of oyster shell and purple cracked jade is calcite structure, 

and the prismatic layer of other shells is aragonite structure. 

3.3  

The “Outline of Conchology” believes: That the Stratum corneum of a shell is composed of only 

conchiolin. This theory is flawed. Most of them have calcite structure, and a few have aragonite 

structure! 

 

 



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3.4  

Shinjiro Kobayashi, a Japanese scholar, proposed in 1959 that prismatic pearls have a calcite structure 

in his “Pearl Research”. Why does prismatic pearls lack luster? Because its nacreous thickness is 

a=0.384 millimeters, the normal nacreous thickness is b=0.613 millimeters (thicker nacreous layers can 

reach 0.92 millimeters or more), with many fewer layers, resulting in a lack of birefringence effect, 

resulting in a lack of pearl luster and oil luster. It also causes the pearl nucleus to have strong reflection 

light, and after interference, it appears earthy yellow. This is the reason why prismatic pearls lack pearl 

luster. 

3.5  

From the X-ray spectra of the Corbiculidae, Corbicula maxima pearl layer, prism layer, and keratin 

layer of the clam shell buried in the ground for thousands of years, it can be seen that the structure of 

aragonite is developing towards a higher degree of crystallization-“single crystal”, indicating that the 

aragonite grains are getting larger and more stable over time. 

3.6  

Modern shells contain some calcite, but ancient shells have almost no calcite. After a long period of 

time, calcite has turned into aragonite in shells! 

The records in geological crystallography books and textbooks are incorrect. 

3.7  

Other ancient shells besides the Corbicula maxima shells also have changes in decreasing, narrowing, 

and strengthening spectral lines over time. However, shells that are too thin and not completely layered 

are easily affected by the stratum corneum. It is better to use thicker shells for detection! 

3.8 The Rest of the Ancient Shells Are Small and Not Easily Stratified 

3.9  

X-ray diffraction from the prismatic layers of ancient shells once again confirms that the prismatic 

layers of shells are all aragonite structures. 

 

Funding 

90 year old commemorative works III 

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 

Image Pearls”  

Chen Guiqing, Chen Junhao 1989 (Approval number 890xx). 

 

 

 



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References 

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. (1986). A study on the natural pearls and shells of Pinctada 

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

Chen, G. Q., Chen, J. H., & Zhang, X. J. (1985). X-ray diffraction study on the shell of Jinjiang oyster. 

Marine Medicine, 1985(3), 4-6. 

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

Shellfish. Jinan University Press. 

Chen, J. H., & Chen, G. Q. (2019). The Ancient Shells Were Sdudied 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 

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

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

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

Crystallography and Mineralogy. Beijing: Geological Publishing House. 

Zhang, X., & Qi, Z. Y. (1961). Outline of Conchology. 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

