The sapphire to be treated is placed into a crucible (left). Generally only one stone per crucible is treated. The crucible is then packed tightly with graphite powder. The graphite not only produces a reducing atmosphere, but also ensures that the heat of the furnace is equally distributed.
{"Image ImageWidth": "581", "Image ImageLength": "773", "Image BitsPerSample": "[8, 8, 8]", "Image PhotometricInterpretation": "2", "Image Orientation": "Horizontal (normal)", "Image SamplesPerPixel": "3", "Image XResolution": "220", "Image YResolution": "220", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CC 2019 (Macintosh)", "Image DateTime": "2019:02:21 08:46:03", "Image ExifOffset": "236", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "386", "Thumbnail JPEGInterchangeFormatLength": "6226", "EXIF ExifVersion": "0221", "EXIF ColorSpace": "Uncalibrated", "EXIF ExifImageWidth": "581", "EXIF ExifImageLength": "773"}