Nacre (L31)

Question 1

What is Mother of Pearl a common term for?

Answer 1

The lustrous, irdiescent material forming the inner surface of seashells

Question 2

What is the Nacre?

Answer 2

The material comprising mother of pearl

Question 3

What are the 3 invertebrate groups that Nacre production includes?

Answer 3

The Bivalves
Gastropods
Cephalopods

Question 4

What are the 5 things that most molluscs possess?

Answer 4

A fleshy foot (used for locomotion)
A radula (rasping organ for feeding)
A digestive system with a stomach and gut
Gills
Mantle

Question 5

What is the mantle?

Answer 5

a fleshy membrane of tissue that surounds the visceral mass.

in molluscs without an external shell, such as squids, the mantle is basically the skin

it also protects delicate internal tissues

AND most importantly it plays a role in shell secretion

Question 6

What do the mantle secrete and then cover?

Answer 6

secretes prisms of calcium carbonate

then covers the layer with tablets of aragonite nacre

Question 7

What happens when shell secretion is not taking place?

Answer 7

the mantle seperates from the shell, so seawater fills the gap in between

Question 8

What is Periostracum?

Answer 8

an organic material deposited and provides protection from dissolution, and aids in camoflauge

Question 9

Why do prismatic and nacreous layers have diff optical properties and what are they?

Answer 9

due to differences in crystal habit

the prismatic layer - weakly translucent to opaque
the nacreous layer - shiny, translucent and often colorful

Question 10

Wht are Nacre largely composed of?

Answer 10

Largely, but not entirely, composed of aragonite crystals and films of organic matter and water

Question 11

what are the tiny tablets of aragonite in nacre glued to adjacent tablets with?

Answer 11

Conchiolin represented by the dark lines

Question 12

What are the 2 things that the quality of lustre in nacre is a function of?

Answer 12

First, the quality of surface reflection (determines the brilliance of the lustre)

second, the quality of internal reflection also influences lustre

Question 13

What is Orient?

Answer 13

The iridescent play of colors in nacre

Question 14

what is one contribution to orient?

Answer 14

the splitting of light waves (diffraction) into individual colors at the spectrum due to the regular arrangement of grooves and ridges on a surface

Question 15

What happens when individual crystals of aragonite act as tiny prisms?

Answer 15

refracts light and disperses it into the colours of the rainbow

Question 16

What is thin firm interference?

Answer 16

the incoming light waves and the reflected light waves constructively interfere in such a way as to produce diff interference colors at diff angles of viewing

Question 17

What is a popular aesthetic practice?

Answer 17

to remove teh outer prismatic layer of a shell to reveal the mroe attractive, shiny, nacreous layer underneath

Question 18

What is Nautilus?

Answer 18

one of the most famous photographs ever made

Question 19

What is a gemostone that has recently entered the gemstone market?

Answer 19

Ammolit

Question 20

Why is Ammolite, Fossil ammonite nacre rare?

Answer 20

b/c under normal preservational circumstances, aragonite either dissolves or is recrystallized to the more stable form of calcium carbonate, calcite

Question 21

Why is the Bearpaw Shale greatly enhanced in intensity of color?

Answer 21

the bold colors are produced due to loss of organic layers between the sheets of aragonite which otherwise limit the transmission of light through nacre and cause the milker appearance of mother of pearl in unfossilized modern molluscs

Question 22

Why is ammolite so hard to work with?

Answer 22

it readily splits apart along planes between aragonite sheets and is quite soft and prone to scratching

Question 23

Most ammolite is mounted in ____ form

Answer 23

Triplet

Question 24

How will you typically see ammoite in a jewellery store?

Answer 24

as a ammolite triplet cabochon