Mineral inclusions in diamonds provide an important source of information about the composition of the continental lithosphere at depths exceeding 120 -150 km, i.e., within the diamond stability field. Fossilized high pressures in coesite inclusions from a Venezuela diamond have been identified and measured by using laser Raman and synchrotron x-ray microanalytical techniques. MicroRaman measurements on an intact inclusion of remnant vibrational band shifts give a high confining pressure of 3.62 (؎0.18) GPa. Synchrotron single-crystal diffraction measurements of the volume compression are in accord with the Raman results and also revealed direct structural information on the state of the inclusion. In contrast to olivine and garnet inclusions, the thermoelasticity of coesite favors accurate identification of pressure preservation. Owing to the unique combination of physical properties of coesite and diamond, this ''coesite-in-diamond'' geobarometer is virtually independent of temperature, allowing an estimation of the initial pressure of Venezuela diamond formation of 5.5 (؎0.5) GPa.S pecimens of Earth materials from great depths often contain mineralogical or textural clues, such as metastable highpressure polymorphs or characteristic mineral assemblages implicating their high-pressure genealogy (1-3). The actual pressure, however, is seldom preserved and observed. For such observations, the sample must be retained in a strong container with appropriate relative thermoelastic properties, and nondestructive analytical techniques must be developed to probe the fossilized pressure condition in situ in the container. Diamond is the strongest possible container. Infrared absorption spectroscopy has been used as the probe for fluid inclusions in diamond (4), and high residual pressures have been reported on the basis of infrared spectra of quartz and CO 2 inclusions in the material (5, 6). In these studies, bulk spectra of diamond and numerous microscopic inclusions were measured; pressures and phases of different inclusions were not determined individually. Herein, we present direct measurements of pressures up to 3.6 GPa in individual coesite inclusions in diamond, a thermoelastic couple most favorable for pressure preservation. We use micro-Ramanand micro-single-crystal x-ray diffraction techniques to probe the pressure of each inclusion separately and precisely. Application to coesite inclusions in diamond from Venezuela provides a determination of the pressure-temperature (P-T) conditions of its formation.Diamond and its inclusions contain rich information about the petrogenesis and geochemistry of the Earth's deep interior (7,8). Although coesite-and diamond-bearing rocks (9-12) undoubtedly have a high-pressure origin, individually, coesite and diamond cover a wide P-T domain of stability (13, 14) that precludes their use as a precise and accurate geobarometer, because they give only a lower bound on the pressure of formation. In many cases, much higher pressures are suggested (15) based on mineral equilibria d...

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