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What are some properties that determine the shape of a crystal?
The shapes of crystals are determined by a number of factors such as the size and length of their surfaces (known as ‘faces’) and edges, as well as the angles between these. These shapes are named after their geometry – for example, crystals based on cubes belong to the ‘cubic or isometric’ crystal group.
What properties help identify quartz?
| Physical Properties of Quartz | |
|---|---|
| Chemical Classification | Silicate |
| Mohs Hardness | 7 |
| Specific Gravity | 2.6 to 2.7 |
| Diagnostic Properties | Conchoidal fracture, glassy luster, hardness |
What are the mineral properties?
Most minerals can be characterized and classified by their unique physical properties: hardness, luster, color, streak, specific gravity, cleavage, fracture, and tenacity.
Which of the following crystal forms have the least number of faces?
A dipyramid has at least 6 faces that meet in points at opposite ends of the crystal. These faces can completely enclose space, so a dipyramid is closed form.
Why do crystals have regular faces?
As a crystal grows, new atoms attach easily to the rougher and less stable parts of the surface, but less easily to the flat, stable surfaces. Therefore, the flat surfaces tend to grow larger and smoother, until the whole crystal surface consists of these plane surfaces.
How many shapes do crystals have?
There are seven basic crystal shapes, also called lattices. They are Cubic, Trigonal, Triclinic, Orthorhombic, Hexagonal, Tetragonal, and Monoclinic.
How do you identify a quartz crystal?
How to Identify Quartz
- A glassy luster.
- Hardness 7 on the Mohs scale, scratching ordinary glass and all types of steel.
- It breaks into curved shards rather than flat-faced cleavage fragments, meaning it exhibits conchoidal fracture.
- Almost always clear or white.
How are the angles between crystal faces plotted?
The following rules are then applied: All crystal faces are plotted as poles (lines perpendicular to the crystal face. Thus, angles between crystal faces are really angles between poles to crystal faces. The bcrystallographic axis is taken as the starting point.
How is the spherical projection of a crystal measured?
Note again that the ρangle is measured in the vertical plane containing the caxis and the pole to the face, and the Φangle is measured in the horizontal plane, clockwise from the baxis. Generally, it is the angles of the spherical projection, ρand Φ, that are given for each face of a crystal.
How are the ρand φangles measured in a crystal?
As an example, the ρand Φangles for the (111) crystal face in a crystal model is shown here. Note again that the ρangle is measured in the vertical plane containing the caxis and the pole to the face, and the Φangle is measured in the horizontal plane, clockwise from the baxis.
How to know which faces on different crystals are the corresponding faces?
In order to know which faces on different crystals are the corresponding faces, we need some kind of standard coordinate system onto which we can orient the crystals and thus be able to refer to different directions and different planes within the crystals.