ORTHOCERAS ANCIENT FOSSIL 65 CTS [MGW 997 ]

4204

存貨單位
尺寸（毫米）: x x mm
重量 (cts)
Certified Gemstones: 不
顏色

Orthoceras

Orthoceras was a ancient mollusk that lived more than 400 million years ago. The name means straight horn, referring to the characteristic long, straight, conical shell. The preserved shell is all that remains of this ancestor of our modern-day squid.

THIS SPECIMEN IS VERY WELL POLISHED .

orthoceras drawing

WEIGHT: 65 CTS APP

SIZE: 53 X 18 X 8 MM APP

The soft body lived in the last open-ended segment at the large end of the conical shell. As the body grew and the housing segment became too small, a dividing wall, called the septa, grew to separate the old “home chamber” from the new one. The differences in the composition of these shell parts allowed for differences in fossilization so the parts can be seen.

The siphuncle is a tube that runs the entire length of the shell, through each of the chambers. This tube had two functions. Once filled with water, the nautiloid could force the water out, propelling itself backward with a kind of jet propulsion. By releasing the water and leaving air space, the tube could serve as a bouyancy device allowing the animal to rise and lower itself to different depths.

These straight shelled nautiloids ranged in size from less than a centimeter to more than 14 feet long!

AS WITH ALL OUR STOCK YOU MAY RETURN IT FOR A FULL REFUND IF NOT PLEASED PROVIVED IT IS NOT TOUCHED IN ANY WAY.

Type 1 Gemstones

The following gemstones are typically inclusion free, even minor inclusions detract from their value.

Diamond, Amethyst, Beryls(Aquamarine,Morganite), Citrine, Smoky Quartz, topaz, Chrysoberyl, Kunzite, Tanzanite, green Tourmaline, and Blue Zircon

IF	Internally flawless under extreme magnification (Very rare)
F	Flawless
VVS	Minute inclusions under 10x; invisible to the unaided eye
VS	Minor inclusions under 10x; usually invisible to the unaided eye
SI1	Noticeable inclusions under 10x; usually visible to the unaided eye
SI2	Noticeable inclusions under 10x; usually quite visible to the unaided eye
I1	prominent- moderate affect on appearance or durability
I2	prominent - severe affect on appearance or durability
I3	prominent- severe affect on beauty, transparency or durability

Type 2 Gemstones

Gemstones that normally have small inclusions that do not detract from value.

Alexandrite, Andalusite, Iolite, Peridot, Rhodolite, Ruby, Sapphire, Spinel, Tourmaline, Garnet, Amethyst, Red Zircon, Tsavorite; Blue, Orange, Purple, Fluorite.Yellow and Parti-colored Tourmaline

F	Flawless
VVS	Minor inclusions under 10x; usually invisible to the unaided eye
VS	Noticeable inclusions under 10x; often invisible to the unaided eye
SI1	Obvious inclusions under 10x; visible to the unaided eye
SI2	Obvious inclusions under 10x; very apparent to the unaided eye
I1	prominent - moderate affect on appearance or durability
I2	prominent - severe affect on appearance or durability
I3	prominent - severe affect on beauty, transparency or durability

存貨單位
尺寸（毫米）: x x mm
重量 (cts)
Certified Gemstones: 不
顏色