Mineralogy Lab 6
X-ray Diffraction
Name _______________________________Last time you received the printouts of your Powder X-ray diffraction run. You have had plenty
of practice with calculating d-spacings, so the computer’s calculations of the d’s are provided as
well. One task remains: the identification of your sample.
1. Recall the color of your sample. That is the color of the streak.
2. Arrange the d-spacings from most intensity to least. In some cases the program will
calculate two d’s in the same general peak. Use the larger one. Use the tens and hundreds
decimal place, but remember, there is an error in the hundreds digit of about +z- 1
3. Look through the red Mineral Powder Diffraction File: Search manual. This is the taller
of the two, with fewer pages.
4. Near the middle will be pages with the d-spacing for your most intense peak in the first
column. Scan down until you find records for your second peak. Remember to include
minerals that differ +/- 1 hundredths. Include synthetic minerals; they are used for central
values of pure minerals. Your sample will be a little off.
5. Check that the third intensity d is approximately correct.
6. When you have a good match, check in your text that the color of the streak is correct for
that mineral. Then write down the mineral name, formula, and file number, here:
7. Turn to the red Mineral Powder Diffraction File: Data Book. This is the thicker of the
two. In the back, page 1341, is an index. Find the page of your file number. Go to that
page and find the card with your file number.
8. Write down the Crystal System, the unit cell dimension(s), and which zones [hkl] gave
the largest reflections, here:
9. If your mineral is Isometric (=”cubic”) check the unit cell dimension using the d for the
most intense peak. Show your work: