Petrographic examination of suites of potsherds can help classify them based on the composition and texture of the rock and mineral particles added to clay for strengthening the product. Such a classification can be used with archaeological studies on form, types of glazing, and other cultural characteristics to help distinguish pottery from different sources. In some cases, the suite of materials added is characteristic of a certain geographical region, so specific source areas can be identified which could indicate ancient trade routes.
Petrographic examination of materials suspected to be from ancient buildings, stelae, or other artifacts can be compared with materials from suspected source areas. If these are similar, one could conclude that the material in question did indeed come from the suspected source area or a geologically very similar and probably closely spatially related source area.
Asbestos in Construction Materials
When old buildings are being demolished or refurbished, it is important to know if the wallboards or other materials contain asbestos. Asbestos may be a deleterious material in other applications as well, including building stone and carving stone. Petrographic analysis and X-ray diffraction studies are used to identify asbestos and determine its abundance.
Ceramics and Glass
Examination of source materials of feldspar and nepheline syenite for possible use in the ceramic and glass industries. The examination determines the amounts of deleterious minerals and their textures, and comments on whether they can be easily separated by simple methods (e.g., magnetic separation).
Petrographic and X-ray Diffraction analysis are used to identify and classify clay minerals.
Concrete and Aggregate Analysis
Field Geological Studies
Field geological studies of potential quarry sites or active quarries help determine the suitability of the material for production of aggregates, and will identify any problem areas in the quarry (strong joint and fracture zones, dikes, alteration zones) that need to be avoided or separated before the aggregate is prepared.
Aggregate Analysis (according to ASTM Standard Test C-295)
This analysis is used to determine the suitability of aggregate for use in concrete or road or dam ballast. The analysis reports on the distribution of shapes, sizes, and expected reactivity of aggregate particles, classifies them petrographically, examines coatings on aggregate particles, and comments on any deleterious material present in the sample.
Porosity Analysis (according to ASTM Standard Test C-457)
This analysis examines the abundance, sizes, and shapes of pores in hardened concrete according to recognized industry parameters.
Problems related to Abrasion or Unusual Wear of Concrete
Petrographic examination helps to understand and explain problems related to concrete wear through chipping, flaking, and other types of degeneration as a result of acid leaching, chemical reactions between particles and cement, and physical wear.
Field Geological Mapping
Field Mapping and assessment of mineral potential in most geological environments both in North America and other countries. Expertise can be provided in solving problems related to ore deposits, structural geology, petrology, regional geology, geochemistry and deposits of industrial minerals.
Petrographic examination of source rocks and crushed material to determine the abundance, grain size, and texture of graphite, and the suitability of source materials for production of commercial-grade graphite concentrates.
Indicator Mineral Picking
Samples are processed in two stages:
- Stage 1: Hand-Sorting of Indicator Minerals: Diamond indicator-minerals are hand-sorted at Vancouver Petrographics Ltd. from heavy-mineral concentrates received from the Process Research Associates.
- Stage 1:Grains picked are catalogued, mounted on slides and polished to electron probe analysis specifications.
Hand Sorting of Indicator Minerals $35.00 CAN per hour
Following is the brief description of hand-sorting processes.
Indicator Minerals: Pyrope Garnet, Magnesiam ilmenite, Chrome Diopside and Chromite and other minerals.
Indicator minerals are hand-picked using established picking techniques. The number of grains are counted for each sample and entered into the data base. Depending upon the objective of the project, coarsest fractions are generally chosen for hand-sorting of minerals.
Scanning Electron Microscope/Electron Probe Analysis
Based on the interest of the client these analysis can be done at reasonable rates. Rates will depend on mineral type and number of grains to be analyzed.
Mounting and Cataloguing - $0.50 CAN per grain
Polishing for Probe 100-200 grains - $40.00 CAN
Probe Work - $7.00 - 8.00 CAN (average cost per grain estimated - call for quote)
The content of water-soluble clay minerals in many kimberlites makes them very difficult to preserve in thin sections. Vancouver Petrographics has developed methods that produce a 99% success rate for this type of sample. We can produce super-thin, 10-20 Microns, slightly wedged sections, commonly referred to as the "Scott-Smith style", that many geologists find useful to help identify diagnostic minerals in highly altered kimberlites.
The meteorites in the following suite of samples were classified into the following main groups:
- Agoult - fine grained gabbro (intergrowth of plagioclase and clinopyroxene with minor sphene.
- Dimmit 1 - native iron and pyrrhotite altered moderately to oxide
- Roosevelt County - native iron and pyrrhotite altered strongly to oxide
- Forrest B1
- Kunya Urgench - native iron and pyrrhotite relatively fresh
- Umbarger - native iron and pyrrhotite altered moderately to oxide
- NWA1084-CR2 - native iron and pyrrhotite altered moderately to oxide
- NWA -984 LL4 - native iron and pyrrhotite altered strongly to oxide
- NWA002-EL6 - native iron and pyrrhotite altered strongly to oxide
- NWA 399 - not brecciated, native iron and pyrrhotite altered moderately to oxide
- Selma H4 - pyrrhotite altered moderately to oxide
- Suizhou - dunite/peridotite, with scattered coarser grains of orthopyroxene in olivine, abundant, relatively fresh native iron and pyrrhotite(?).
- Banded /Peridotite/Dunite/Norite
- Bondoc ME5 - sharply banded with layers from one end to the other as follows:
- peridotite: megacrysts of orthopyroxene intergrown with much finer grained olivine
- extremely fine grained dunite
- norite/anorthosite: plagioclase in part with megacrysts of orthopyroxene
- abundant native iron and lesser pyrrhotite, mainly replaced by hematite/limonite
Examinations are made of source materials and products of materials such as rutile and wollastonite to determine their suitability for use in the paint and related industries. Studies examine textures regarding clarity of materials and their ease of separation from the host rock, degree of purity of products, and aspect ratios (for wollastonite).
Petrographic Descriptions (not including sample prep)
Detailed descriptions are of Polished Thin Sections in reflected light (for opaque minerals) and transmitted light, and of Thin Sections in transmitted light only. The basic cost per section includes ONE photograph. Normally, ONE to FOUR photographs are taken per section to illustrate pertinent petrographic features. Please specify if photos are NOT required, otherwise they will be included. Please supply as much geological information as possible and list any specific questions you have regarding the samples. The more information you give us, the more we will be able to help you. For example, inclusion of a sample location map and geological map will help us to help you interpret spatial and genetic relations between samples.
For a suite of samples, the report will include a summary (in which samples are classified and specific questions by the client are answered), detailed descriptions of each sample (some very similar samples may be grouped), and photographs accompanied by descriptions of the photographs. When enough background information is supplied by the client, the summary report also will include comments regarding genesis of the samples where appropriate.
Detailed descriptions include interpreted rock name, visual modal analysis, description of mineral texture, size, and alteration, texture and mineralogy of replacement patches and veins, deformational events, and relative ages of features. Photographs illustrate pertinent textures and mineral relations. Where possible, hypothesis of genesis will be made.
Identification of some minerals may require the Scanning Electron Microprobe or X-ray Diffraction. Before doing such studies, we will advise you if they are appropriate for mineral identification in your samples and consult you regarding timing and cost.
Rock Cutting and Polishing
Rock Cutting is $0.70 per square inch (minimum $2.00 per sample).
Rough polish (saw marks ground off) $.20 per square inch.
Display Polishing is $10.00 for the first square inch, and $1.25 for each addition square inch.
Rock Fill Analysis
Petrographic examination of source rocks and crushed material to determine the suitability for fill. Analysis includes petrographic analysis, determination of size-and shape-distribution of crushed materials, identification of deleterious components (e.g., sulphides, water -soluble materials).