Petrography is the detailed examination of rocks including the analysis of fluid inclusions.

Petrography is the detailed study of rocks, most commonly on the microscopic scale.  Such studies can include simple imaging, measuring the luminous intensity with a microscope photometer, or the transmission, reflectance and even fluorescence spectra with a microscope spectrophotometer.  Some of the most common applications are fluorescence microspectroscopy of fluid inclusion, vitrinite reflectance of coal and kerogens as well as the spectral analysis of gemstones and minerals.

CRAIC Technologies offers a number of petrographic solutions.  These include purpose built systems such as the CRAIC CoalPro II™ Vitrinite Reflection Measurement System to the 308 Coal™ and 20/30 PV™ for advanced microscopic imaging and spectral analysis of petrographic samples.

To learn more about the science behind petrographic analysis, select one of the following links: 

What is a mMcrospectrophotometer?

Science of Microspectrophotometers

CRAIC CoalPro II™ Measurement System

308 Coal™ Spectrophotometer for your Microscope

20/30 PV™ Microspectrophotometer



Measuring the Energy Content of Coal

Vitrinite Coal

Optical Petrography

Coal is made up a macerals.  Macerals are the organic component of coal, kerogen or other petroleum source rocks.  Examples of macerals include vitrinite, inertinite and liptinite.  Vitrinite is one of the primary components of coal, petroleum source rocks and  sedimentary kerogens. Under a microscope, it has a shiny appearance and is derived from the cell-wall material or woody tissue of plants.  Since vitrinite changes predictably with heating (over geological time periods), vitrinite reflectance levels are a reliable measurement of a coal sample's thermal maturity thus its value as a source of energy.  As such, methods have been developed to measure the percentage of reflected light from a coal sample and to determine the thermal maturity or rank of the coal sample and thus the energy content of that sample.  Vitrinite reflectance measurements are also used on petroleum source rocks and sedimentary kerogens to measure their thermal maturity and thus the type of petrochemicals that they contain.  Reflectance values between 0.5 to 1.3% are considered optimal for these types of samples.

How to Measure Vitrinite Reflectance

The measurement of vitrinite reflectance is defined by both ISO and ASTM standards methods (as well as other national standards).  ISO 7404-5 and ASTM D2798 both state that measuring the vitrinite reflectance of coal is to be done with a specially configured microscope using a calibrated photometer.  The microscope is configured for incident illumination with green light where the illuminating light may be either plane-polarized or not.  The reflected light intensity is measured with either a photometer, a spectrophotometer or with a digital camera fitted to the microscope. 

The system is calibrated with special Vitrinite Reflectance Standards, supplied by CRAIC.  The sample is then placed on the sample stage and brought into focus.  Using the standard methodology, at least 100 measurements are made of the sample.  This allows the user to test blends that contain coals of different ranks.  From the data, the mean and standard deviation of all the readings are calculated as percent reflectance.  The spread of the individual reflectance values is also plotted as a histogram.  This allows the user to determine the different macerals and types of macerals in a sample.  This data will give an indication of the rank of the coal sample.

For more detail on vitrinite reflectance, visit the following pages:

ISO 7404-5 Method of Determining MIcroscopically the Reflectance of Vitrinite
Vitrinite Reflectance by CRAIC


The Raman Microscope Spectrometer is designed to measure Raman spectra of microscopic samples or microscopic areas of larger objects.  The fully integrated Raman microscope spectrometer has been built and optimized for microspectroscopy and is capable of measuring the Raman spectra of microscopic samples.  

The CRAIC Technologies™ Raman microscope spectrometer is a purpose-built system that allows you to analyze Raman microspectra™ non-destructively and with no sample contact.  Capable of analyzing even microscopic areas, they are also capable of color digital imaging.  Designed for ease-of-use, they are durable instruments designed for microscale Raman spectroscopy.

To learn more about Raman microspectroscopy and the CRAIC Technologies Raman microscope spectrometer, select one of the following links: 

The Science of Raman Microscope Spectroscopy

How a Raman Microscope Spectrometer is Used

CRAIC Apollo Raman Microscope Spectrometers

We invite you to discover our revolutionary technologies that include a Raman microscope spectrometer, microspectrometers, UV-visible-NIR microscopes, Traceable Standards, microscope spectrometer accessories and software. We further invite you to experience our exceptional service and technical support.

Lambdafire Microspectrometer Software



Sophisticated software for microspectrophotometer control, spectra and image analysis




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Perfect Vision for Science™



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Lambdafire™, CRAIC Lambdafire™, Lambdafire II™, CRAIC Lambdafire II™, the lit microscope base and the lit octagonal optical head are trademarks of CRAIC Technologies, Inc. CRAIC Technologies, 20/20™, 20/20 PV™ and "Perfect Vision for Science" are all trademarks of CRAIC Technologies, Inc. Instrument features offered depend upon instrument configuration.  Features listed here may not be present in some configurations.

*Features and specifications depend upon instrument configuration.  Specifications subject to change without notice.

UV-visible-NIR microscopes, UV-visible-NIR microspectrometers and Raman microspectrometers are general purpose laboratory instruments. They have not been cleared or approved by the European IVD Directive, the United States Food and Drug Administration or any other agency for diagnostic, clinical or other medical use.

Lab On A Chip Analysis

Lab on a chip analysis with a microspectrophotometer

Microspectrophotometers are used to analyze lab-on-a-chip test points by reflectance, absorbance and fluorescence


Lab on a chip analysis with a microspectrophotometer

Typical test spectra



Rapid spectral analysis of microscopic test areas in Lab On A Chip devices.

Lab On A Chip devices, sometimes called microfluidic devices, are designed to replicate a series of full-scale chemical and biological reactions on a single micro-scale device.  They are sometimes called microelectromechanical systems (MEMS) for their fluid handling capabilities on the microscopic scale.  As such, a single device is used replicate a series of chemical reactions but on a microscopic scale.  Therefore analytical techniques are required that can measure whether reactions have reached a successful conclusion but of micro-scale volumes.

  Able to analyze micro-scale volumes by absorbance, reflectance or even fluorescence, microspectrophotometers are easy-to-use and very accurate.  Their flexibility and accuracy make them very important when developing or using custom lab-on-a-chip devices. 

To learn more about microspectroscopy and lab-on-a-chip development and testing, select one of the following links: 

What is a Microspectrophotometer?

Science of Microspectrophotometers

Microspectrophotometer Design

Uses of Microspectrophotometers

20/30 PV™ Microspectrophotometers