Calcium oxalate crystals grow in a variety of habits depending on the plant and the part of the plant in which the are found. The shapes shown here lead to examples of similar shapes in different plants or parts of plants. Prisms include cubes, rectangles, and bipyrimidal prisms. Rhombs include diamond shapes and various rhomboid single crystals. Twins include a variety of twinned shapes. Druse includes rosets and crystal agglomerates. Cell shapes are included here as constrained druse structures though that is not necessarily the case. Raphid includes single raphids, raphid clusters, and styloids.

. . . . Prisms . . . . . . . . . . . . Rhombs . . . . . . . . . . Twins . . . . . . . . . . . . Druse . . . . . . . . . . . Raphid

KINGDOM: Plantae UNRANKED: Angiosperms UNRANKED: Eudicots UNRANKED: Core Eudicots ORDER: Caryophyllales FAMILY: Polygonaceae GENUS: Rumex SPECIES: crispus

Leaves

KINGDOM: Plantae DIVISION: Pinophyta CLASS: Pinopsida ORDER: Pinales FAMILY: Pinaceae GENUS: Larix SPECIES: occidentalis

KINGDOM: Plantae DIVISION: Pinophyta CLASS: Pinopsida ORDER: Pinales FAMILY: Pinaceae GENUS: Pseudotsuga SPECIES: menziesii

From a Forest Fire

Leaves

Bark

Acorn Cap

Pyrolized calcium oxalate phytoliths are a marker for forest fire smoke, or any industrial, commercial, or other activity that involves the burning of plant material containing a concentration of calcium oxalate phytoliths. They have been used to identify homes impacted by wildfires, businesses impacted by emissions of restaurants, towns impacted by slash burns, Teepee burners, hog-fuel boilers, etc. The predictable chemical changes that take place as a result of short exposure to high temperatures often result in a particle with characteristic optical properties and a shape reminiscent of the original phytolith.

Whewellite, the most common form of calcium oxalate in plants (CaC₂O₄-H₂O) begins looseing water at about 120 degrees Celsius. At aout 420 Celsius it begins forming calcium carbonate with the loss of carbon monoxide. At about 620 celsius it begins forming calcium oxide with the loss of carbon dioxide. The final form of the pyrolized calcium oxalate is dependent on the amount of time at temperature. In a wildfire that time is often rather short and results in a chemical modification of the surface of the phytolith.