GEM KNOWLEDGE · LABORATORY NOTES
Tai Chi Quartz
“Tai Chi Quartz” is a market name attached to this Chinese carved tower, also sold as Taiji Stone and sometimes as jade or anhydrite. The laboratory findings tell a different geological story.
Finding: Sample 9250 showed high-magnesium calcite. The darker areas approach, but do not reach, stoichiometric dolomite. Quartz grains and likely organic components are also present. No sulfur was detected, so the specimen is not anhydrite. The researcher described it as silty, high-magnesium calcite-bearing limestone, possibly grading toward fine-grained marble.
Why it matters: Neither “quartz” nor “jade” is an accurate name for the whole tested carving. The report describes quartz grains within a carbonate-rich rock, not a quartz or jade specimen. These results apply to this submitted piece, not to everything sold under either trade name.
Tested specimen: Chinese tower submitted January 15, 2021; report completed January 25, 2021. See also Taiji Stone for the alternate market name.
View the original report
Select a page to enlarge it. 2 pages; findings are summarized in accessible text above.
Read the original laboratory report as text
The following text and tables are transcribed from the original laboratory document. Figure captions identify the report images; the laboratory interpretations and limitations are preserved.
Laboratory report 1
Analytical Result Report
Sample id: 9250 (Chinese tower -said to be anhydrite)
Submitted by: K. Bitner
Date submitted: Jan. 15, 2021.
Date completed: Jan. 25, 2021.
Operating conditions: JEOL JSM-6400 operated at 25 kV acceleration potential, 15 mm working distance, 15 degrees sample tilt, coated with 250 Å carbon. Using the X-ray fluorescence attachment with 35kv potental in conjunction with the EDS system.
Fig. 1: Photograph of the specimen, approximately 6 cm tall.
Fig. 2: Petrographic photomicrographs of the acid-insoluble residue of the specimen. Left: plane polarized light, right: with crossed Nichols. Width of view: 750 microns.
Fig. 3: Effervescence of the specimen in contact with 10 % hydrochloric acid showing bubbles of carbon dioxide being released.
Table 1: Compositions of the specimen (In weight percent)
| element | Light gray area | Dark gray area |
|---|---|---|
| Silicon dioxide | 8.5 | 11.36 |
| Aluminum oxide | 0.70 | 1.04 |
| Calcium oxide | 38.7 | 30.5 |
| Magnesium oxide | 7.53 | 15.4 |
| Iron oxide | 0.07 | 0.09 |
| Sulfur trioxide | Not detected | Not detected |
Summary of findings: Surprise, the specimen (Fig. 1) is not anhydrite! It contains nor detectable sulfur!
It is a high magnesium calcite; the dark areas are getting close to dolomite but do not quite make it to stoichiometric dolomite. The sample still effervesces with cold diluted acid which dolomite does not do easily. There are silt-size particles of quartz present as well (Fig. 2). The darker color of some of the bands is likely due to organic components. A pretty specimen but just not anhydrite.
In summary, this could be called a silty, high-magnesium calcite-bearing limestone or a slightly metamorphosed one that is grading into fine-grained marble.
Date: January 25, 2021 Signature