Figure 3. Transmitted-light photomicrographs of Lake Fryxell carbonates showing acicular calcite crystals forming botryoids (A) and interfering bundles (B) at depths of 9.0 and 9.7 meters, respectively. Adjacent zones of crystals often grow in different directions. Sediment and organic matter (dark-colored zones) are commonly found surrounding and interspersed throughout carbonates. Scale bars are 100 μm. Arrows indicate direction to mat-water interface.