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Frequently Asked Questions (FAQ)

GENERAL | XRF ANALYSIS | MISCELLANY | LAB BLOG INDEX

THIS SECTION IS CURRENTLY UNDER DEVELOPMENT AND CURRENTLY REMAINS A LITTLE ROUGH AROUND THE EDGES

GENERAL LAB QUESTIONS
  • Just what DO you do at the lab?
  • What's the turnaround time for results?
  • I'm in a real hurry - can I rush things?
  • What about the summer lab schedule?
  • What kind of a report do I get?
  • I need an electronic version of the report - any problem?
  • I need the data on disk - any problem?
  • I need the data on a spreadsheet - any problem?
  • How do I find more information about obsidian (or FGV/basalt) sources that are identified?
  • How much does it cost?
  • I'll be needing several different reports for the artifacts that I'm sending - how do I determine the per sample price rate?
  • Will I have to pay for samples that turn out to be too small after analysis?
  • Will I have to pay for samples that turn out to not be obsidian or that are non-volcanic?
  • How do I arrange payment?
  • What's the best way to ship artifacts to the lab?
  • What geographic source areas are well covered by Northwest Research?
  • I'm having trouble reading the lab Adobe Acrobat documents you sent - what can I do?
  • Are the old lab reports available online or can I order them from you?
  • How long have you been doing this kind of work?
  • What happened to the old BioSystems Analysis obsidian lab?
  • What happened to the obsidian hydration laboratory?
  • Do you plan to retire and close the lab?
  • XRF TRACE ELEMENT ANALYSIS QUESTIONS
  • How does XRF (X-ray fluorescence) analysis work?
  • Is XRF analysis destructive?
  • In addition to obsidian, what kind of other lithic materials can be characterized using XRF analysis?
  • Does XRF analysis make samples radioactive?
  • How do you assign sources to the analyzed artifacts?
  • What does it mean when there's an unknown source assignment?
  • How do you locate unknown geologic sources?
  • How can I check to see if you've located an unknown source that was identified in a previous trace element study?
  • Is there a minimum physical sample size?
  • Will dirt or painted sample numbers on the artifacts affect the analysis?
  • How about sample selection strategies for XRF analysis? How much is enough?
  • What can I do with the source data once I have it?
  • What kind of variables influence the geographic patterning of geochemically-characterized artifacts?
  • What kind of spectrometer do you have at the lab?
  • MISCELLANEOUS QUESTIONS ABOUT OBSIDIAN OR FINE-GRAINED VOLCANIC (FGV) MATERIALS
  • How is obsidian formed?
  • Why is obsidian black?
  • Why is obsidian colors other than black (mahogany, green, etc.)?
  • What causes the iridescence (rainbow sheen or chatoyancy) in some pieces of obsidian?
  • I have something that I think is obsidian but how can I tell for sure?
  • Do you have any maps showing the locations of obsidian sources?
  • Why don't you simply put all the obsidian sources locations on Google Maps
  • How do I get obsidian source locations?
  • Can I make a telescope mirror out of obsidian?
  • Can I melt obsidian and pour it into a mold?
  • Are obsidian scalpels really sharper than metal instruments?
  • I live next to a deposit of obsidian - is there any way I can make some money with it?
  • What is an FGV?
  • How can I tell if a rock is a basalt, andesite, rhyolite, or dacite?
  • Do you offer opportunities for internships or student practicums?
  • How do you get the high-resolution images of artifacts?
  • How do I figure out the distance from a site to an obsidian source?
  • SOURCE AND LAB BLOG INDEX
  • A New Nevada Obsidian Source: Robinson Summit
  • Lost and Found in British Columbia: Central Coast A
  • Parke Creek Tachylyte: Washington's Newest Obsidian Source
  • Tall Tales from the End of the Trail 1
  • Tall Tales from the End of the Trail 2
  • Top 5 and Top 10 Obsidian Source Lists
  • Top 5 Obsidian Sources: Colorado
  • Top 5 Obsidian Sources: Washington
  • Top 10 Obsidian Sources: California
  • Top 10 Obsidian Sources: Oregon
  • Top 10 Obsidian Sources: Utah
  • Unknown X: Found at Last
  • Unknown X: The Back Story

    Stay Tuned: It's been a while since the blog has been updated but it hasn't been forgotten!
  • HAVE ANY QUESTIONS THAT YOU DON'T SEE HERE? LET US KNOW AND WE'LL POST THE ANSWERS

    ANSWERS: GENERAL QUESTIONS
    JUST WHAT DO YOU DO AT THE LAB?

    Using an EDXRF (energy-dispersive X-ray fluorescence) spectrometer, I nondestructively analyze obsidian (and sometimes fine-grained volcanic) artifacts and determine the trace element profile (or signature) of the glass. This unique pattern is compared to a reference library of analyzed obsidian sources and the geologic source of the artifact can then be determined.

    WHAT'S THE TURNAROUND TIME FOR RESULTS?

    It's typically four to six weeks, although it can potentially run longer when I'm backed up with work, am having hardware problems, or during the summer field season (see below). I recommend that you give me as much lead time as possible - I'm constantly analyzing new source material and a relaxed turnaround schedule will ensure that I'll have time to analyze any newly sampled sources in your site region. Spectrometer hardware problems are very infrequent but can potentially delay project completion from several days to several months. If you have contract deadlines that must be met, let me know what they are as far in advance as possible and I'll be glad to work with you to meet them. I'll also be happy to send you a draft copy of your results in advance of the final report.

    If you don't need a standard final report but will be happy with only the source assignments, data tables, and a data CD, your project turnaround time can often be cut significantly. While the standard final report makes a nice-looking appendix, everything in it beyond the individual project data is available through the lab website. In the case of multi-stage and/or multi-year projects, I'll be happy to provide a comprehensive and updated final report at the end of the project. Let me know.

    I'M IN A REAL HURRY - CAN I RUSH THINGS?

    Sure thing. I have a special rapid turnaround rate for those of you in a big hurry. For an extra 35%, I'll drop everything else, forsake my families and friends, and focus on your job. Within two weeks, you'll have a copy of the results emailed to you. The extra charge covers overtime and strained relationships with my family and other customers. For obvious reasons, a two week turnaround may not be practical for rather large jobs or for the other reasons mentioned in the previous discussion of expected turnaround time. If you're absolutely counting on the rapid turnaround to meet a project deadline, it's essential to contact me in advance.

    WHAT ABOUT THE LAB SUMMMER SCHEDULE?

    Please note that the regular and rapid turnaround during the summer months from June 1 to September 1 is likely to be irregular. During this period, I'm engaged in hardware maintenance, catchup, cleanup, recovery, and, most importantly, summer fieldwork. I maintain an active summer field schedule and am often out of the office during this period. However, I will regularly be in the lab during these months and will be checking the voicemail while we're out so don't hesitate to call for information or for help with projects. That said, I'm rarely very far away from laptops and iPhones and email is almost always the most reliable way to find me.

    WHAT KIND OF REPORT DO I GET?

    Unless you request only the discounted (-10%) Basic Report (data tables and data disk), I'll send you a short final report in a format suitable for use as a report appendix. Our final report includes a brief description of our obsidian characterization and hydration methods, a summary of the results of the analyses, the locations and descriptions of any sources that were identified, and a copy of all data in table format. Due to the increasing accessibility of the World Wide Web, I'm now supplementing lab reports with increasing amounts of up-to-date information available through the lab Web sites at www.obsidianlab.com and www.sourcecatalog.com and through the International Association for Obsidian Studies Obsidian Source Catalog.

    For downloadable samples of the Regular and Basic lab reports, click HERE.

    I NEED AN ELECTRONIC VERSION OF THE REPORT - ANY PROBLEM?

    Not at all. Each project report (regular or basic) is also produced as an Adobe Acrobat (PDF) document which will be emailed to you as soon as we've completed it. A report in this format may be read with the free Adobe Acrobat reader that can be downloaded from Adobe - click HERE to download the Acrobat software.

    I NEED THE DATA ON DISK - ANY PROBLEM?

    Again, no problem. Your data is always included on disk along with your final report - in Excel (.xls), Quattro (.qpw), and comma-delimited (.txt) file formats. If you have any special data file needs, let me know and I'll try to accommodate you.

    I NEED THE DATA ON A SPREADSHEET - ANY PROBLEM?

    And once again, no problem. I always include a copy of the data spreadsheet when I return a project and usually send along an Excel spreadsheet when you're notified that your project is done.

    HOW DO I FIND MORE INFORMATION ABOUT OBSIDIAN (OR FGV/BASALT) SOURCES THAT ARE IDENTIFIED?

    Try any of the following locations for information about specific source and obsidian-related resources that are available through the Internet. These locations also all accessible through the Northwest Research Home Page.

    U. S. Obsidian Source Catalog
    International Association for Obsidian Studies (IAOS) Web Site
    IAOS Obsidian Source Catalog

    HOW MUCH DOES IT COST?

    The price rate is based on the number of samples submitted. Prices last went up on June 1, 2011, and will stay that way for several more years. For the latest price break, you can download an Adobe Acrobat version of the price sheet and sample submission form.

    I'LL BE NEEDING SEVERAL DIFFERENT REPORTS FOR THE ARTIFACTS THAT I'M SENDING - HOW DO I DETERMINE THE PER SAMPLE PRICE RATE?

    WILL I HAVE TO PAY FOR SAMPLES THAT TURN OUT TO BE TOO SMALL AFTER ANALYSIS?

    No - I won't charge you for samples that turn out to be too small for XRF analysis. I carefully examine each artifact prior to analysis and will reject any samples that are clearly too small. If I'm not sure, I will attempt to analyze them and will not charge you if I am not successful.

    WILL I HAVE TO PAY FOR SAMPLES THAT TURN OUT TO NOT BE OBSIDIAN OR THAT ARE NON-VOLCANIC?

    Yes - I'll charge you for samples that turn out to be non-obsidian or, in the case of FGV's, that are non-volcanic. However, I keep an eye out for duds when loading samples and won't charge you for anything that I'm able to catch before analysis. If I suspect that samples are non-volcanic but aren't certain, I'll attempt to analyze them and will not charge you if I am not successful.

    HOW DO I ARRANGE PAYMENT?

    I'll send you an invoice when I return your analyzed artifacts. I accept checks, cash, PayPal, and selected credit cards (Visa and Mastercard).

    WHAT'S THE BEST WAY TO SHIP ARTIFACTS TO THE LAB?

    I generally ship artifacts using UPS or Fedex - each shipment is assigned a tracking number that can be followed online. Certified mail is also an easy option and may be more convenient in some areas (use a return receipt if you want to be notified that your shipment has bee received). Artifacts for shipment are generally packaged in ziploc bags in a protective box with plenty of bubble wrap and/or styrofoam peanuts, a technique that works well to protect your valuable artifacts. It's always a good idea to place a return address inside the box in case the label gets torn off during shipment. Top this off with a liberal application of nylon strapping tape and the safe shipment arrival of your samples is almost guaranteed.

    WHAT GEOGRAPHIC SOURCE AREAS ARE WELL COVERED BY NORTHWEST RESEARCH?

    In general, obsidian source coverage is restricted to the western United States and British Columbia, Canada, and the Western Mediterrean. Coverage for most regions of Oregon, California, Nevada, Washington, Idaho, Utah, Colorado, Wyoming, New Mexico, Arizona, and British Columbia is very good. The lab source database for Alaska is growing but is still patchy. I also occasionally work with volcanic glasses in other geographic areas including Mexico and the Western Mediterranean (good coverage here), the Far East, Russia, and several Pacific Islands. If you're curious to see what geographic areas have been included in recent (1995 and on) reports, click HERE. If you're not sure whether or not our source database is adequate for your artifacts, call or e-mail and I can provide more details and/or referrals to other labs. To see which specific sources that I use in correlating artifacts and sources, see the obsidian source reference database list. The lab geochemical source research program is quite active and new sources are constantly being added to the reference database.

    I'M HAVING TROUBLE READING THE LAB ADOBE ACROBAT DOCUMENTS YOU SENT - WHAT CAN I DO?

    No worries ... you probably need a simple upgrade to a newer version of the new free Acrobat Reader. You can download a copy at the Adobe Reader website.

    ARE THE OLD LAB REPORTS AVAILABLE ONLINE OR CAN I ORDER THEM FROM YOU?

    HOW LONG HAVE YOU BEEN DOING THIS KIND OF WORK?

    The BioSystems Obsidian Lab was originally organized by Thomas Jackson and Robert Jackson (no, they're not related), two California archaeologists who had become interested in obsidian characterization and hydration studies in the 1970's. The obsidian lab really got rolling in 1992 with the purchase of a Spectrace 5000 energy-dispersive XRF spectrometer. In late 1994, Tom and Rob left BioSystems to form Pacific Legacy, Inc., a California company specializing in cultural resource management. At that point, Craig Skinner (who had been working primarily with Oregon obsidians since 1981) was hired to manage the XRF and obsidian hydration labs. To date, well over 80,000 obsidian and basalt artifacts (plus several thousand source samples) have been analyzed at the lab. For the post-BioSystems chapter in the story, see the next question.

    WHAT HAPPENED TO THE OLD BIOSYSTEMS ANALYSIS OBSIDIAN LAB?

    The BioSystems Obsidian Studies Laboratory began as a division of BioSystems Analysis, a firm whose parent office was located in Santa Cruz, California. When Craig came on in late 1994 to look after the obsidian labs, the XRF Lab was located in Santa Cruz and the hydration lab was situated in Sacramento. In late 1995 and early 1996, the two labs were reunited in Corvallis, Oregon. Kathy Davis, the XRF analyst in Santa Cruz, also initially moved north with the spectrometer. Jennifer Thatcher, our longtime obsidian hydration analyst, started in Corvallis immediately after the move and was trained by Jay King, the previous BioSystems obsidian hydration analyst (he and Kathy Davis are now married and they and their two children are living in Sacramento, California). Shortly thereafter, BioSystems Analysis fell into financial difficulties and bankruptcy court. I took over management of the labs, changed the name to Northwest Research, made an offer for the lab assets, and finally bought the whole works in late 1996. Much of the staff and hardware remain the same and only the name was initially changed. All the original BioSystems obsidian-related records, obsidian and FGV source reference material, and archived obsidian hydration slides are safely stored here in Corvallis.

    WHAT HAPPENED TO THE OBSIDIAN HYDRATION LABORATORY?

    As of January 1st, 2014, the obsidian hydration lab lives on as Willamette Analytics and is now owned and operated by Jennifer Thatcher, longtime hydration analyst for Northwest Research. I continue to maintain a close relationship with Jennifer and Willamette Analytics and I'll be happy to forward any artifacts on to her after XRF analysis is complete.

    DO YOU PLAN TO RETIRE AND CLOSE THE LAB?

    This question has come up lately and the answer is a qualified no. That said, I am planning to slow down the pace of the lab considerably and I'll be out of town catching up on field work and recreation much more often in 2014 and 2015. For the immediate future, Northwest Research will continue to operate as a commercial service as I make the transition to a more research-oriented and part-time business. At some point in the relatively near future, I'll also entertain the possibility of selling the lab and all assets to a qualified buyer although I have no specific details or timeline available at the present. At that point in time, if there are no interested parties, I'll continue to operate the lab and spectrometer as a research-only venture and will eventually distribute the obsidian and FGV reference collection to several interested universities.

    ANSWERS: XRF TRACE ELEMENT ANALYSIS QUESTIONS
    HOW DOES XRF (X-RAY FLUORESCENCE) ANALYSIS WORK?

    With XRF spectrometry, the specimen is bombarded with X-rays or high-energy electrons from a conventional X-ray tube located in the spectrometer. This causes a disturbance of the electron orbitals of atoms and the sample then emits secondary or fluorescent X-rays of wavelengths that are then detected with our spectrometer. The resultant spectra lines or peaks (see the figure below) are characteristic of the elements present in the specimen. The height of the peaks is directly proportional to the amount of each element - these are converted to quantitative parts per million figures by comparing them with rock standards of known chemical composition.

    IS XRF ANALYSIS DESTRUCTIVE?

    No. Aside from the fact that I may have to scrub or scrape away surface residues, you'll never know the artifact has been analyzed. The best candidates for nondestructive XRF analysis are artifacts that are of adequate sample mass (see below) and that have a relatively flat and clean surface available for analysis. While it's possible the increase the accuracy and precision of the analysis by using finely powdered samples that have been pressed into pellets, a considerable body of research now exists that demonstrates that nondestructive analysis of obsidian and fine-grained basalt artifacts is a very viable characterization method.

    IN ADDITION TO OBSIDIAN, WHAT KINDS OF OTHER LITHIC MATERIALS CAN BE CHARACTERIZED USING XRF ANALYSIS?

    DOES XRF ANALYSIS MAKE SAMPLES RADIOACTIVE?

    No. Samples may be safely handled immediately after analysis.

    HOW DO YOU ASSIGN SOURCES TO THE ANALYZED ARTIFACTS?

    Geologic source are assigned to artifacts by correlating the trace element composition of the artifact with sources contained in the lab source reference database. This database currently contains data for well over 100,000 analyzed source samples and artifacts and is continually updated with additional trace element data. Alternative correlation methods that are sometimes also used in provenience studies also include statistical techniques (cluster and principal components analysis) and graphical methods (bivariate scatterplots or ternary diagrams, for example). The visual appearance of the artifact may also be occasionally used to verify or reject an artifact source, although I never rely on visual methods except in a very minor way.

    WHAT DOES IT MEAN WHEN THERE'S AN UNKNOWN SOURCE ASSIGNMENT?

    An unknown source assignment can be attributable to three likely causes: (1) The source is simply not contained in our source reference database, (2) The trace element composition of the analyzed sample fell well outside of the range of variability of our source reference samples, or (3) There was an analytical problem of some kind.

    To deal with the first two issues, I maintain a very active source research program and generally analyze a minimum of 15 source samples (when available). When sources with considerable variability are encountered, I continue to analyze samples until I'm satisfied that I understand the expected range of trace element values and variation.

    Analytical problems may be instrumental (spectrometer malfunction) or may be related to a specific sample problem (uneven surface geometry, surface residue, presence of phenocrysts in glass, small sample size). When I suspect that there may be an analytical problem of some sort, I often reanalyze suspect samples to try and isolate the source of the problem. Each set of analyzed samples also includes a monitor standard so that I can immediately spot and pinpoint instrumental difficulties.

    HOW DO YOU LOCATE UNKNOWN GEOLOGIC SOURCES?

    Sometimes I'm just lucky and stumble across an unknown source during routine summer field work or find one when archaeologists send in source samples for analysis. More often, I wait and watch for geographic patterns of groups of unknowns to develop. By examining relative frequencies of unknown sources at dispersed archaeological sites (or geologic sampling locations), geologic maps, and geomorphic clues (e.g., drainage patterns), I have been able to so far chase down all but the most persistent mystery sources.

    HOW CAN I CHECK TO SEE if you've located an unknown source that was identified in a previous trace element study?

    Easy. Just email or call and I'll be happy to see if we've found the source since your project was completed. Let us know the site name, lab project number, and specimen number(s) and we'll review our source reference database to see if any new sources have shown up on our radar.

    IS THERE A MINIMUM PHYSICAL SAMPLE SIZE?

    Yes. Extensive experimentation in our laboratory has demonstrated that the absolute minimum size requirements for accurate trace element determinations of most samples is at least 1 cm in (minimum) diameter and 1 mm in thickness. Slightly larger samples will yield more robust trace element values and I prefer to analyze specimens at least 1.5 cm in diameter and 2 mm in thickness whenever possible. In any case, I do not recommend the use of small samples in complex source areas or regions where the source universe is poorly understood.

    WILL DIRT OR PAINTED SAMPLE NUMBERS ON THE ARTIFACTS AFFECT THE ANALYSIS?

    They often can. What I'm actually analyzing is the surface layer of the artifact - if there's dirt, patina, or some encrustation present, the analysis will reflect the trace element composition of that material as well as the artifact. Because of this, the surface of the items to be analyzed should be clean and preferably free from labels or residues. A simple wash with tap water and a toothbrush will usually suffice for the job. However, if artifacts already have painted sample numbers, the numbers may be left intact - even when paint is removed, some residue is left behind and it's better if the location of the number is obvious. Interference to the analysis by paint, when it occurs, is usually reflected in elevated levels of titanium, zinc, or lead. Particularly persistent residues may be removed with an X-acto knife.

    HOW ABOUT SAMPLE SELECTION STRATEGIES FOR XRF ANALYSIS? HOW MUCH IS ENOUGH?

    Different classes of artifacts will tend to reflect different procurement behaviors and patterns. In general, formed tools such as projectile points will tend to come from a wider variety of sources (higher source diversity) than unformed, utilitarian artifacts or debitage (lower source diversity). If you're looking at local raw material use, select debitage. To look at quarry behavior, choose cores. If you're looking for evidence of longer-distance procurement or interaction, you'll probably want to pick formed tools. Similarly, the analysis of temporally diagnostic projectile points may add a valuable dimension of time to the analysis.

    More samples = greater source diversity. In other words, larger numbers of analyzed artifacts tend to yield larger numbers of different individual sources. The number of different geochemical sources of obsidian or basalt that are identified at a given site are affected by numerous environmental and cultural variables, most notably the number of available sources, their relative distance to the site, and the number of artifact samples that are characterized. In areas of low source diversity (e.g., southern California), few sources were used and a modest number of samples will provide a good overall idea of the range and proportion of sources that were used. In areas of high source diversity (e.g., the Fort Rock Basin of Oregon), many sources of obsidian were utilized and it will take a proportionately larger number of samples to reconstruct an accurate scenario of overall procurement patterns.

    Also see the back side of the lab price list for another brief discussion of sample selection strategies.

    WHAT CAN I DO WITH THE SOURCE DATA ONCE I HAVE IT?

    WHAT KIND OF VARIABLES INFLUENCE THE GEOGRAPHIC PATTERNING OF GEOCHEMICALLY-CHARACTERIZED ARTIFACTS?

    WHAT KIND OF SPECTROMETER DO YOU HAVE AT THE LAB?

    It's a ThermoElectron QuanX EC EDXRF spectrometer: The old Spectrace 5000 EDXRF spectrometer was permanently retired in 2012.

    Click on the title at the top of the videos to view this clip and more on YouTube.

    ANSWERS: MISCELLANEOUS QUESTIONS ABOUT OBSIDIAN OR FINE-GRAINED VOLCANIC (FGV) MATERIALS
    HOW IS OBSIDIAN FORMED?

    WHY IS OBSIDIAN BLACK?

    WHY IS OBSIDIAN COLORS OTHER THAN BLACK (MAHOGANY, GREEN, ETC.)?

    WHAT CAUSES THE IRIDESCENCE (RAINBOW SHEEN OR CHATOYANCY) IN SOME PIECES OF OBSIDIAN?

    I HAVE SOMETHING THAT I THINK IS OBSIDIAN BUT HOW CAN I TELL FOR SURE?

    DO YOU HAVE ANY MAPS SHOWING THE LOCATIONS OF OBSIDIAN SOURCES?

    Yes - with the help of Jennifer Thatcher at Willamette Analytics, I've begun to produce obsidian source maps for most of the western states. Click HERE to see what's available.

    WHY DON'T YOU SIMPLY PUT ALL THE OBSIDIAN SOURCES LOCATIONS ON GOOGLE MAPS?

    HOW DO I GET OBSIDIAN SOURCE LOCATIONS?

    CAN I MAKE A TELESCOPE MIRROR OUT OF OBSIDIAN?

    Yes, although I'm not sure why anyone would want to. A 1954 article by Theodore Dunham, Studies of Obsidian as a Material for Making Astronomical Mirrors, describes the successful use of obsidian mirrors up to 31 inches in diameter.

    CAN I MELT OBSIDIAN AND POUR IT INTO A MOLD?

    Nope. When obsidian is heated, it will turn into a foam (like pumice) because of the intrinsic water content of the glass.

    ARE OBSIDIAN SCALPELS REALLY SHARPER THAN METAL INSTRUMENTS?

    According to Wikipedia, the edge of an obsidian blade can be as little as three nanometers thick, significantly sharper than a comparable metal edge. See the abstract of the article they cite (Disa et al. 1993) for more details.

    I LIVE NEXT TO A DEPOSIT OF OBSIDIAN - IS THERE ANY WAY I CAN MAKE SOME MONEY WITH IT?

    Obsidian is common enough so that it's value as a raw material is not very much - perhaps only a few dollars per pound. It's only when the glass is transformed into something - jewelry, beads, carved figurines, pendants, boxes, spheres, knives, wind chimes, and so on - that it may gain some value. Take a look at eBay for some ideas. As an aside, please note that not everything represented on eBay as obsidian - particularly the colored and very transparent glasses - is the real thing.

    WHAT IS AN FGV?

    A fine-grained volcanic rock. These can include lower-silica rocks like basalts and higher-silica materials such as rhyolites and dacites. What they all have in common is a fine-grained texture that's free of inclusions and phenocrysts. HOW CAN I TELL IF A ROCK IS A BASALT, ANDESITE, RHYOLITE, OR DACITE?

    See the explanation at our FGV lab page. DO YOU OFFER OPPORTUNITIES FOR INTERNSHIPS OR STUDENT PRACTICUMS?

    HOW DO YOU GET THE HIGH-RESOLUTION IMAGES OF ARTIFACTS?

    HOW DO I FIGURE OUT THE DISTANCE FROM A SITE TO AN OBSIDIAN SOURCE?

    This sounds like a straightforward question but can get a little tricky to answer clearly. In our experience, the most common reasons for determining the distance of an artifact to its source is for (1) the construction of distance-decay graphs and (2) to explore the procurement distance variable in terms of its cultural significance. More on this later.

    Back to the Obsidian Lab Home Page

    Last Updated: 09/02/2014
    Northwest Research Obsidian Studies Laboratory