Amorphous-to-Crystalline Transition of Ca–Mg-Carbonates as a Function of Composition, Time, and Temperature
Bibliographic record
Abstract
Calcium and magnesium carbonate minerals play an important role in regulating Earth’s climate, and they are among the most common biominerals. Growing evidence suggests that some natural biotic and abiotic calcium and magnesium carbonate minerals precipitated from amorphous precursors. Here, we synthesized amorphous carbonates with different molar ratios of Ca and Mg ( n = 6 compositions from 0–100 mol % Mg). We then examined their crystallization under water-limited conditions (i.e., in dry air) as a function of time and at two temperatures (23 and 75 °C). Experiments were performed under dry conditions to slow the amorphous-to-crystalline transition so that it could be studied in detail. Our results show that the mol % Mg in amorphous calcium magnesium carbonates controls the rate of crystallization in air and the resulting complex mineral assemblages. We found that considerable amorphous material remains after more than 1 year, particularly for intermediate compositions near 50 mol % Mg. Room temperature crystallization in air is faster for Ca-bearing amorphous phases. Our results provide new insights that are applicable to biomineralization, the complex mineralogy of carbonate sediments and in developing methods to sequester CO 2 in minerals, particularly under water-limited conditions.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".