CRYSTALLOGRAPHY

The crystallography tool is a measurement oriented tool and very accurate provided you know the various crystallographic properties your mineral possesses. Similarly to Optical before it, Crystallography requires you to know advanced crystallographic constants and how to obtain them from your mineral. The properties supported are Crystal Systems, Crystal classes, Hermann-Mauguin symbols, Space groups, Unit cell dimensions, Unit cell angles, Unit cell volume and Unit cell density. If you know any one of these properties, the tool will be able to perform a database comparison versus known mineral crystallographic data. Tapping the always persistent floating button on the lower right will immediately start a database search based on your checked options.

Symmetrical Properties

Minerals have the following properties in regards to symmetry…

1. One of the 7 crystal systems.

2. One of the 32 crystal classes.

3. At least 1 H-M symbol.

4. At least 1 of the 230 space groups.

Those properties serve as a foundation for crystal system classification. The crystal system property uses a cascading dropdown sequence of menus to deliver a simplified selection process of the properties above. This is due to the interdependent relationship between systems, classes and space groups. That is, systems determine the classes, and classes determine the H-M symbols and space groups. To choose your crystal system, start by…

• Tapping the 'Crystal System' checkbox to activate the 'Crystal system' dropdown menu below it.

• Tap the 'Crystal System' menu to see the 7 crystal systems.

• Select one of the seven systems to complete your selection.

Each of the seven crystal systems in turn has its unique groups of crystal classes. 

• After selection of your system, a secondary dropdown menu will activate with Crystal classes specific to your choice system.

• Tap it to see the available classes.

• Select any class to complete your selection.

• Choosing a class will display its Hermann-Mauguin (International) symbol on a banner.

Your crystal class choice will additionally have its unique selection of space groups.

• After choosing a class, another tertiary dropdown menu with Space groups will activate.

• Tap it to see available space groups.

• Choose any of the space groups marks the end of selection for 'Crystal System'.

This tree of selection is maintained by the tool. Should you choose another crystal system, the tool will respond by collapsing all your previous options and restarting the selection process. Please note that it’s not necessary to select the complete system, class, space group combination. If you know only the System, it should be enough to perform a database search by leaving other options unselected.

Additionally, specific crystal systems may disable several unit cell dimensions if they are inapplicable. For example; the cubic (isometric) system has all axes being equal to the a axis and all angles at 90°. Because of this, b and c axis become disabled as well as all cell angles.

Unit Cell dimensions

Unit cells have several dimensions which are unique (in most cases) to each mineral. These are the crystallographic axes (a, b and c) and crystallographic angles (alpha, beta and gamma). Our database contains these measurements on several thousands of minerals hence it's possible to perform a comparison search. To do so, follow the following procedure applicable for all measurements…

• Tap your choice dimension checkbox to activate a text input field below it. Example: tapping the 'C axis' checkbox will activate a checkbox below it, allowing you to input the search parameter for your mineral c-axis.

• Input your dimension on the provided text input area.

• Repeat for any other dimension you may want to search for.

Additionally, the unit cell dimensions have extra search properties for 'Volume' and 'Density'. These are the unit-cell volume and density of the mineral. The same procedure applied above still holds for searching these values as well.

Similarly to other tools, cell dimensions text fields contain filters to verify what you give them. Input outside these restrictions will result in a computational failure. The filters in use are…

• Positive numbers only for the crystallographic axes, volume and density.

• Positive and less than or equal to 180 for crystallographic angles.

Crystallography card

When satisfied with your search parameters, tap the floating button at the lower right of the tool to begin a search. If results are found, you will receive a list of cards matching all your parameters. The cards will also provide a summary of the properties it has. Tapping any of the cards will direct you to the 'Mineral details' page of the mineral you tapped.