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EARTHSCI 1089G > WEEK 12 - Types of Pearls > Flashcards

WEEK 12 - Types of Pearls Flashcards

1
Q

Pearl Oysters vs. Edible Oysters

A
  • Pearl oysters make nacreous pearls.
  • Edible oysters can make pearls but they are porcelaneous, not nacreous.
  • Pearl oysters secrete nacre, while edible oysters do not.
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2
Q

What are nacreous pearls?

A

Pearls made by pearl oysters.

Composed of layers of nacre (mother of pearl).

Shiny, iridescent appearance.

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3
Q

What are porcelaneous pearls?

A

Pearls produced by edible oysters.

Not made from nacre.

Often dull and lack iridescence.

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4
Q

Which critters can make pearls?

A

Many molluscs can make pearls.

Includes bivalves (e.g., mussels), gastropods (e.g., conchs), and cephalopods (e.g., Nautilus).

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5
Q

What is required for high-lustre (nacreous) pearls?

A

High-lustre (nacreous) pearls are only produced by molluscs with a nacreous layer.

Nacreous pearls are shiny and iridescent.

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6
Q

Q: Which molluscs do not produce nacreous pearls?

A

Conchs and blue mussels do not secrete nacre.

Their pearls are not nacreous.

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7
Q

What is the “Pearl of Puerto”?

A

Irregular porcelaneous blister pearl produced by a giant clam (Tridacna).

Collected in 1996 off the coast of Palawan Island, Philippines.

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8
Q

Characteristics of “Pearl of Puerto”

A

Length: 67 cm.

Width: 30 cm.

Weight: 34 kg (75 pounds).

Estimated value: $100 million USD.

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9
Q

Where was the “Pearl of Puerto” found?

A

Found by a Filipino fisherman off the coast of Palawan Island, Philippines.

Kept under his bed for 10 years as a lucky charm.

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10
Q

What is the “Giga Pearl”?

A

Recently unveiled by Abraham Reyes of Mississauga.

Contained within a giant clam purchased by his grandfather from a Filipino fisherman.

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11
Q

How long was the “Giga Pearl” kept before being publicly revealed?

A

Clam was kept by Reyes’ aunt since 1959 as a family heirloom.

Publicly revealed in 2019.

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12
Q

What was commissioned for the “Giga Pearl”?

A

Sculptor Bethany Krull was commissioned to create a gold-gilded brass octopus to hold the pearl.

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13
Q

Characteristics of “Giga Pearl”

A

Weight: 27 kg (60 pounds).

Estimated value: $90 million USD.

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14
Q

What determines the colour and lustre of a pearl?

A

The colour and lustre match the characteristics of the nacreous layer of the host shell.

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15
Q

What are nacreous pearls made of?

A

Composed of nacre, built by epithelial (surface) cells of mantle tissue.

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16
Q

How does a pearl form?

A

A foreign body irritates the mantle tissue, and the mollusc surrounds it with smooth layers of nacre to reduce irritation.

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17
Q

What typically forms the nucleus of a pearl?

A

Rarely grains of sand.

More commonly, it is a foreign body that cannot be expelled by the mollusc.

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18
Q

How are the layers of a natural pearl structured?

A

Layers of aragonite are separated by layers of conchiolin.

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19
Q

What gives a pearl its warm glow?

A

Light penetrates through the pearl, giving it a warm glow throughout.

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20
Q

What are blister pearls?

A

Pearls that adhere to the nacreous layer of the shell.

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21
Q

How do blister pearls form?

A

When an irritant (often a parasite) gets trapped between the shell and the mantle tissue, and the mollusc covers it with nacre.

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22
Q

What happened in the case where nacre was secreted around a clam?

A

Nacre was secreted around a clam that managed to bore into an abalone shell from the outside.

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23
Q

What is the unique example involving a fish and pearl oyster?

A

A fish got trapped between the mantle and nacreous surface of a pearl oyster, and nacre covered the fish, forming a blister.

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24
Q

How are free pearls formed?

A
  • Less readily than blister pearls
  • When an irritant is completely surrounded by nacre-secreting epithelial cells of the mantle and held away from the nacreous layer of the shell
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25
How rare are free pearls in the wild?
Only 1 in 10,000 oysters will contain a pearl in the wild A small percentage of these pearls will be of gem quality.
26
How do natural free pearls form?
When a parasite invades, stimulating an invagination of the epithelium. Epithelial tissue surrounds the invader, creating a pearl sac in the deeper levels of the mantle. Nacre is secreted around the invader, forming a free pearl.
27
Where can natural free pearls be formed?
Can form deep within mantle tissue or in the gonad if epithelial cells are moved there by the invading parasite.
28
What properties are valued in pearls?
Lustre, colour, and orient
29
How does lustre in pearls form?
Depends on high reflectivity and internal reflection of light.
30
What determines the colour of a pearl?
The basic colour of a pearl (body colour) is influenced by pigments in conchiolin. Conchiolin colour varies between species of pearl oysters.
31
What is the difference between dark and white pearls?
Dark pearls (e.g., Tahitian) have thick layers of dark-coloured conchiolin. White pearls (e.g., Akoya) have thin layers of light-coloured conchiolin.
32
What is orient in pearls?
The iridescent play of colours caused by light breaking up into colours of the spectrum.
33
How does orient form in pearls?
Caused by surface relief and the refractive/reflective properties of aragonite layers in the pearl.
34
Can you give an example of orient in a pearl?
The subtle iridescent colours seen in an Akoya pearl, which is grown in the Akoya oyster.
35
How rare are natural free pearls?
About 1 in 10,000-15,000 pearl oysters will produce a natural free pearl.
36
What is the shape of most natural free pearls?
They lack the desired spherical shape but are often irregular.
37
What are Baroque pearls?
Large, irregular pearls that have commanded high prices throughout history.
38
What is the origin of the term "Baroque"?
Comes from the Italian word "barocco," meaning bizarre or strange, and was used to describe pearls before it was applied to art and music.
39
What are fossil pearls?
Rare pearls preserved in the fossil record, usually found in the nacreous layer of shells.
40
How old are the fossil pearls found in London Clay?
50 million years old.
41
Why do some fossil pearls retain their lustre?
They retain their nacreous lustre due to exceptional preservation conditions, especially the lack of dissolution.
42
What is the source of the fossil pearls in London Clay?
Come from pen shells.
43
Who patented the practice of perliculture?
Mikimoto Kōkichi patented perliculture in 1916.
44
How has perliculture affected the availability of pearls?
Perliculture has greatly increased the availability of pearls to consumers.
45
Why was perliculture introduced?
Wild pearl oysters were nearly driven to extinction in Hawaii and Tahiti, and pollution also threatened their populations.
46
What are some advantages of perliculture?
1. Better pearl count to oyster ratio 2. Some control over pearl shape 3. Control over pearl size
47
What is a disadvantage of the perliculture industry?
1. Perliculture is a very labour-intensive industry.
48
How are oysters prepared for tissue implant in the cultured pearl industry?
Oysters are anaesthetized to relax their adductor muscle and open their shell. This allows for the tissue implant necessary for pearl cultivation.
49
How is the tissue and nucleation bead inserted into an oyster for cultured pearls?
Epithelial mantle tissue from donor oysters is cut into small strips. A slice of mantle tissue and a nucleation bead (often from freshwater clams) are inserted into the gonad of the recipient oyster, away from the nacreous layer of the shell.
50
How does a cultured pearl begin to form?
A pearl sac forms in the gonad after tissue and a nucleation bead are implanted.
51
How does the mantle tissue contribute to cultured pearl formation?
The epithelial mantle tissue secretes nacre, covering the bead to form a pearl.
52
What is the difference between natural and cultured pearls?
Natural pearls have more nacre compared to the nucleus. Cultured pearls have a thin nacreous rind surrounding a larger nucleus.
53
What is the minimum nacre thickness for a cultured pearl to be valuable?
The nacreous rind must be at least 15% of the total diameter of the pearl.
54
What is the survival rate of oysters in cultured pearl farms?
500 out of every 1,000 oysters die during the culturing period.
55
How many oysters produce saleable pearls on a pearl farm?
200 out of 1,000 oysters produce saleable pearls of low to medium quality.
56
How many oysters produce top-grade, gem-quality pearls on a pearl farm?
50 out of 1,000 oysters produce top-grade, gem-quality pearls.
57
How long does it take to produce a marketable cultured pearl?
2 years to produce a marketable pearl with a nacre layer of about 0.4 millimetres thick.
58
What is the average size of a Japanese cultured pearl?
7 millimetres.
59
What are Mabé pearls?
A new type of cultured pearl (technically a blister pearl). Created by inserting hollow, flat-bottomed plastic domes between the mantle and nacreous layer of the pearl oyster shell. Oysters secrete nacre on the plastic domes.
60
How are Mabé pearls processed after secretion?
Cut from the oyster shell. The plastic domes are removed. The hollow interior is filled with wax (sometimes colored for tint). A disc of mother of pearl is glued to the bottom for support.
61
What are Mabé pearls typically used for?
Used in jewelry where a spherical shape isn’t necessary. Commonly used in earrings and other flat-backed settings.
62
How old is the blister pearl technique used in Mabé pearls?
Used by Chinese as early as the 5th century A.D. Considered a prototype of modern Mabé pearl technique. Objects were “pearlized” by inserting carved ivory, ceramic, or shell into clams.
63
Are blister pearls still made today?
Yes, China still produces elaborate blister pearls. Modern examples include pearls shaped like Chairman Mao.

EARTHSCI 1089G (32 decks)

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