18 Questions
What was the purpose of carefully selecting sample points on each specimen?
To select relatively flat and smooth areas without large mineral inclusions, in order to mitigate air attenuation.
How did the researchers account for heterogeneity in the mineral inclusions of each stone?
They took three readings across each sample and averaged them together.
What precision did the researchers achieve using this method for fine-grained rocks?
±5% precision.
How did the researchers account for coatings and contaminants on the samples?
They underwent low-impact cleaning with water and a toothbrush for 15 seconds to remove lichen and other contaminants, and allowed them to fully air-dry before taking readings.
How did the researchers validate the efficacy of their cleaning approach?
They selected a control specimen and took a reading in the same location on it each day the equipment was used, in order to calculate error rates for each element of interest and determine the impact of instrument performance variability.
How did the researchers account for inter-year precision when the 2018 standard was difficult to access in 2020?
They selected a second standard of a different stone type and repeated readings on an accessible sculpture that had been analyzed in 2018.
What is the primary purpose of conducting destructive analysis on rock samples?
To obtain accurate measures of percentages of specific minerals or elements within a sample.
Briefly describe the QAPF Modal Classification system for volcanic rocks.
It classifies volcanic rocks based on the relative percentages of the minerals quartz, alkali feldspar, plagioclase, and feldspathoid.
What are the key parameters used in the TAS (Total Alkali-Silica) classification system?
The relative percent weight of silica dioxide vs sodium and potassium oxide.
When is field classification of rocks necessary, according to the passage?
In cases where sample collection and destructive analysis are not possible.
What key factors does the modified 1955 Travis classification system consider for field classification?
Color, texture, and macroscopically visible mineralogy of rocks.
Why does the U.S. Bureau of Reclamation use broad lithological classifications according to the passage?
To account for slight imprecisions in mineral identification that do not affect the mechanical properties relevant for stability.
What is the primary purpose of geochemical analysis via pXRF spectroscopy in the context of this study?
To identify groups of sculptures that use the same raw materials and to compare the MAA sculptures to potential lithic sources in the Huaraz region.
Why was a quantitative approach not used for the geochemical analysis in this study?
The absence of regionally specific calibration data to convert x-ray intensities into concentrations prohibited quantitative analysis.
What alternative approach was used instead of quantitative analysis, and why was it suitable?
A semiquantitative approach utilizing statistical analysis of intensity ratios was used instead of element concentrations, because the ratio between elements within the same pXRF reading should remain fixed, allowing provenance to be assessed.
What are the sequential steps involved in the semiquantitative analysis approach outlined in the text?
The sequential steps are: 1) initial data processing, 2) element and ratio selection, 3) precision validation, and 4) statistical analysis.
Based on the information provided, what is the fundamental principle that allows the use of intensity ratios for provenance assessment in pXRF spectroscopy?
The ratio between elements within the same pXRF reading should remain fixed, allowing provenance to be assessed.
What is the primary advantage of using a semiquantitative approach over a quantitative approach in this study, given the absence of calibration data?
The semiquantitative approach does not require converting x-ray intensities into concentrations, which would have required the missing calibration data.
Test your knowledge on methods used in analyzing minerals and elements in samples, such as the QAPF Modal Classification and the TAS classification system. Learn about obtaining accurate measures of percentages of specific minerals or elements.
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