What minerals have a conchoidal fracture?

What minerals have a conchoidal fracture?

Conchoidal fracture breakage that resembles the concentric ripples of a mussel shell. It often occurs in amorphous or fine-grained minerals such as flint, opal or obsidian, but may also occur in crystalline minerals such as quartz.

What causes conchoidal fracture?

In geology, conchoidal refers to a curved, shell-like shape that certain brittle rocks and minerals exhibit if fractured by a blow. As a result of the radiating shock created by a sharp blow, such fractures have smooth rounded concentric ridges that resemble a mussel shell with its growth lines.

What is conchoidal mineral?

“Conchoidal” (like “conch” a large and edible marine snail) is the term that relates the broken surface of a mineral to the curved surfaces of snails. This particular feature is present in only a few common minerals, such as pyrite, quartz and garnet.

What is a conchoidal fracture pattern?

A conchoidal fracture refers to a haphazard mode of breakage of a material that does not adhere to any fixed or well-described physical planes of separation. Brittle materials are more likely to exhibit conchoidal fracturing.

What is conchoidal fracture and why it is so important for Flintknapping?

These rock types, when struck with another rock, piece of antler, or bone, will fracture or break in a characteristic pattern called a conchoidal fracture. This creates a rock fragment called a flake. Flakes have specific features identifying them as the result of human hands rather than natural processes.

What rock has a conchoidal fracture?

Obsidian is famous for its conchoidal fracture surface. This rock type was highly valued during the Stone Age because it makes a fine cutting blade if treated (fractured by precise and forceful blows) correctly.

What mineral has a greasy feel?

mineral Talc
For example, the mineral Talc always has a greasy feel.

Does quartz conchoidal fracture?

Crystalline materials such as quartz also exhibit conchoidal fractures when they lack a cleavage plane and do not break along a plane parallel to their crystalline faces.

What is the difference between Clechage and conchoidal fracture?

Fracture and cleavage both describe how a mineral breaks. Fracture refers to rough or irregular surfaces along which the mineral breaks randomly. Cleavage refers to flat planes along which some minerals break. Fracture can be described as conchoidal, rough, smooth, or fibrous.

Why does quartz have conchoidal fracture?

However, conchoidal fracture is common in crystalline materials also if they have no cleavage (like mineral quartz), or if they are composed of very small mineral grains so that the fracture surface which is actually zigzagging between the grains appears smooth to our eyes.

What is a blue mineral?

The most common blue/bluish minerals of this type include azurite, chalcanthite, chrysocolla, linarite, opal, smithsonite, turquoise, and vivianite.