Norms (from normalize) are simply ways to recalculate chemical analyses of rocks in order to make some comparisons easier than, or at least different from, comparisons of the chemical analyses directly. The norm program here produces a modification of the standard CIPW weight norm that is most commonly used in geology.
This norm has been modified to group all plagioclase components together, and to combine the normative En, Fs, and Wo components into the Diopside and Orthopyroxene components. SO₃ apportionment has been modified to include anhydrite if there is insufficient Na₂O to make Thenardite. Cr₂O₃ apportionment has been modified to include the Magnesiochromite component if there is insufficient FeO to produce Iron-Chromite.
The norms are calculated and listed under the headings "Weight % Norm" and "Volume % Norm", next to the list of "Normative Minerals". Weight norms are the most commonly used. Beneath the norm columns you'll find other calculated values. More infos about these values are provided by clicking the appropriate info-button.
Enter the chemical composition of the rock in the appropriate fields under the heading "Rock Analysis". You may use the period (".") or the comma (",") as decimal point. If you wish, select one of the three options under "Options" (normalization, logging, Fe-ratio correction). Different elements should be entered in their oxide weight percents, or in elemental parts per million. These measures correspond to the way these elements are usually given in a common chemical analysis.
After a calculation, you should delete all inputs and results with the button "New calculation". This minimizes the processor load when re-entering! Alternatively, you can reload the page.
You can activate the output of the intermediate results in the console. This protocol allows a – essentially – direct comparison with the original Excel file. Normally, logging the intermediate results should not be necessary. This is primarily for debugging.
The chemical analysis can be recalculated to 100% before calculating the norm.
You can set the ratio of Fe3⁺/(Fe3⁺+Fe2⁺) to a constant ratio. Type in a zero or a number between 0 and 1. If zero, the Fe₂O₃ and FeO values in the Rock Analysis column are used in the norm calculation. If a value between zero and one is used, this value is used as the ratio of Fe3⁺ to total iron in the norm calculations.
For more Information about the options please click on the Info-Buttons or the details-elements (▶) on the input page.︎
The "Corrected Analysis" column is derived from the "Rock Analysis" column but includes the changes you requested under "Options".
These values have been corrected as follows:
These are the various normative components (minerals) that the norm program calculates. They are picked to be, in a certain sense, similar to the minerals you might find in an igneous rock slowly cooled at low pressure under dry conditions. In a more practical sense, they are standard components which can be used to compare one rock with another in the same way that chemical analyses can be compared. Don't get the idea that you will actually find all these phases in your rocks.
The weight norm is the standard norm that almost everybody uses. The normative components (minerals) are calculated in terms of their weight percent. This type of norm can not be compared with thin section point count modes.
The volume norm is not usually reported in the literature. In a volume norm the normative components (minerals) are calculated in terms of their volume % in the normative rock, rather than weight %. This type of norm can be compared, in some respects, to thin section point count modes. Just remember that the normative components are pure, whereas real minerals are solid solutions. For example, the normative plagioclase and orthoclase could actually be a single mesoperthite or sanidine in a real rock.
This function uses the values of the calculated CIPW norm minerals. So first you have to do a calculation of the CIPW standard before a rock can be represented in the diagrams. Choose between "Volcanic rock" and "Plutonic rock" according to your sample so that the correct diagram is displayed. If you do not calculate a CIPW standard, after clicking on the button, only the Streckeisen diagrams without a data point are displayed. Explanations can be found in the drop-down box under the diagram.
For this diagram the data of your chemical analysis are used. A calculation of the CIPW standard is therefore not necessary. An input of SiO₂, Na₂O and K₂O is sufficient for a classification with this diagram. After clicking on the button, the diagram is displayed with the data point. The explanations can be found in the drop-down box under the diagram.
The Streckeisen and TAS diagrams can be downloaded as png graphics files. To do this, use the buttons directly below the diagrams.
You have the option of downloading the results of the calculations as a csv file. For example, this format can be easily opened in LibreOffice Calc. The csv file contains all calculated values including the comment. However, the Streckeisen- and the TAS diagram must be downloaded separately (using the buttons below the respective diagrams). Before the download you have to enter a name and an identification (these are also included in the csv file). The downloaded file has a name according to the following scheme: CIPW_TheName_Date.csv.
January 2023; RockClass 1.4: Major changes to the user interface; fixed an Ilmenite / Sphene allocation bug; New function: Streckeisen diagrams can now be created directly without having to calculate the CIPW standard
March 2020; RockClass 2020-03-V1.3: Improved menu: Now works better on mobile devices
March 2020; RockClass 2020-03-V1.2: Minor fixes; Reset-buttons now work correctly
January 2020; RockClass 2020-01-V1: First version
It is recommended to delete all inputs and results with the button "New calculation" before a new calculation. This minimizes the calculation load when re-entering data and avoids erroneous output!
If the automatic norm-check is showing a red warning message there's is a problem with the norm. This may mean that your rock composition was typed in wrong, that the rock composition lies outside the composition space in which the norm is designed to work, or it may indicate a bug in the calculation program. First, check for data entry errors and control the composition of your rock. If this is not the problem, and should you encounter other strange results, or should the app behave otherwise strangely, the cause may be related to the browser cache. In this case, delete the browser cache or the recent history (often via the "History" menu), taking care not to delete important settings (cookies, etc.) as well. Reload the page. In rare cases it might be necessary to quit the browser and to delete the cache manually in the file system. If all this does not help, please contact Minetosh online.
All functions have been tested with: Firefox and Chromium (Google Chrome).
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