Exclusive Aesthetics of Nature
Inclusions in Gemstones
Contact and Information
Michael Hügi, M.Sc., Mineralogist, Gemmologist FGA, Bern, Switzerland
michael-huegi@gemmologie.ch
Swiss Gemmological Society
www.gemmologie.ch
Image Gallery
All images: © Michael Hügi
- 1: Inclusions probably of melanterite (hydrous Fe sulphate) in rock crystal (quartz), from Minas Gerais, Brazil. It is a pseudomorphis after the iron sulphide marcasite, which is also found as inclusions in quartz of the same deposit. Image width: approx. 6 mm, transmitted light, crossed polarizers
- 2: Inclusions probably of melanterite (hydrous Fe sulphate) in rock crystal (quartz), found at Minas Gerais, Brazil. Image width: approx. 4 mm, transmitted light, single polarization
- 3: Natural etch patterns (so-called trigons) on a diamond crystal. Such structures are formed by partial dissolution of the diamond during the ascent of the hot Kimberlitic magma from the Earth’s mantle.. The interference colors are caused by strain birefringence. Image width: approx. 4 mm, transmitted light, crossed polarizers
- 4: Inclusion of a fly in Baltic amber, found on the East Baltic coast. Amber is a fossil resin, and this sample originated about 35 – 40 million years ago in forests in what is now the Baltic region. Amber occasionally contains inclusions of insects, spiders, small vertebrates, etc., which stuck to the resin and were covered by subsequent resin layers. Although amber is an amorphous substance and in theory optically isotropic, the flow structures of the resin due to internal strain as well as the strain caused by the inclusions can be visualized in polarized light. Image width: approx. 4 mm, transmitted light, crossed polarizers, first-order red compensator
- 5: Inclusion of midges in Baltic amber, found on the East Baltic coast.See notes on image no. 4. Image width: approx. 12 mm, transmitted light, crossed polarizers, first-order red compensator
- 6: Inclusion of a fly in Baltic amber found on the East Baltic coast. See notes on image no. 4. Image width: approx. 4 mm, combination of transmitted and incident light (fiber-optics), crossed polarizers, first-order red compensator, HDRI tone mapping
- 7: Fluid inclusions and growth zoning in aquamarine (variety of beryl), found at Padre Paraiso Mine, Minas Gerais, Brazil. During the growth of a crystal in an aqueous solution, stress can cause the formation of fractures that heal as the crystal continues to grow. In the former fissure, remains of the original aqueous solution are sealed in cavities, the so-called negative crystals. These fluid inclusions are located in the plane of the former crack. Their contents separate in different phases as the stone cools down after crystal growth. In the illustrated sample, all inclusions contain a gas bubble (CO2), liquid CO2 and a small amount of water. Image width: approx. 2 mm, transmitted light, crossed polarizers, first-order red compensator
- 8: Fluid inclusions and growth zoning in aquamarine (variety of beryl), found at Padre Paraiso Mine, Minas Gerais, Brazil. See notes on image no. 7. Image width: approx. 3 mm, transmitted light, crossed polarizers, first-order red compensator
- 9:Growth structures (negative crystals) in aquamarine (variety of beryl), found in Tanzania. Beryl crystals generally grow much more quickly in the direction of their longitudinal axis than transversely. This means that even minor irregularities in the crystal lead to the formation of long hollow channels, some of which gradually heal and are terminated by crystal faces (so-called negative crystals). In the image shown, the negative crystals are hexagonal pyramids that have formed on a former crystal surface.Image width: approx. 4 mm, incident light (fiber-optics illumination) in darkfield, single polarization (analyzer)
- 10: Inclusion of a tourmaline crystal in aquamarine (variety of beryl), found in Northern Pakistan. The interference colors of the tourmaline needles are due to the polarized light. Image width: approx. 1.5 mm, transmitted light, single polarization
- 11: Rock crystal (quartz) with rutile needles, trapped in rock crystal (quartz), found at Minas Gerais, Brazil. The image shows a doubly terminated quartz crystal intergrown with bent rutile needles (titanium oxide, TiO2). A second generation of quartz has grown round this crystal. As it has the same refractive index as the host mineral, the inclusion is hardly visible in ordinary light, but easy to detect in polarized light. Image width: approx. 1.2 mm, transmitted light, crossed polarizers, first-order red compensator
- 12: Growth structures (negative crystals) in aquamarine (variety of beryl) found at Minas Gerais, Brazil. Viewing direction almost parallel to the optical axis, therefore interference colors in polarized light. See also notes on image no.9. Image width: approx. 10 mm, transmitted light, crossed polarizers
- 13: Agate found at Reichweiler near Idar-Oberstein, Germany. Agate is the banded variety of chalcedony, which is a microcrystalline variety of quartz. Under the microscope, the reason for the red colour of the bands is revealed as round to lentil-shaped hematite aggregates. The nature of the green branching in the center of the image is still a matter of debate: whereas the traditional school of thought considers it to be inorganic precipitations of dissolved SiO2, more recent examinations point to an organic origin, i.e. fossil algae or bacteria colonies that were able to survive the temperatures of over 100°C required for the formation of agate.Image width: approx. 10 mm, incident light
- 14: Agate found at Reichweiler near Idar-Oberstein, Germany. See notes on image no.13, Image width: approx. 16 mm, incident light
- 15: Inclusions probably of siderite (FeCO3) and rutile needles The color and morphology of the brown rhombohedral crystals suggest with high probability that they are composed of the iron carbonate siderite. The bright interference colors of the otherwise colorless quartz are formed by the almost parallel viewing direction to the optical axis of the crystal in polarized light. Image height: approx. 10 mm, combination of incident light (fiber-optics) and transmitted light, crossed polarizers
- 16: Fluid inclusions and inclusions of rutile needles and small siderite crystals (iron carbonate) in rock crystal (quartz), found at Minas Gerais, Brazil. The irregular cavities formed by growth contain remains of the aqueous solution in which the rock crystal grew about 500 million years ago. The bright interference colors of the otherwise colorless quartz are formed by the almost parallel viewing direction to the optical axis of the crystal in polarized light. Image width: approx. 6 mm, transmitted light, crossed polarizers
- 17: Inclusions of radial goethite aggregates (iron hydroxide) in a fissure in rock crystal (quartz), found at Minas Gerais, Brazil. This is a so-called epigenetic inclusion, i.e. it originated after the growth of the host crystal was completed. In this case, aqueous solutions containing iron entered an open fissure in the crystal. After drying out, the dissolved iron crystallized as aggregates of goethite crystals on the surface of the crack. Due to the radial arrangement of the crystals, a dark cross pattern is formed in each aggregate in doubly polarized light. Image width: approx. 1.5 mm, transmitted light, crossed polarizers
- 18: Inclusions of rutile needles in quartz, Minas Gerais, Brazil. The photographed gemstone of the famous stone cut designer Bernd Munsteiner proves that inclusions in gemstones are not defects but natural features that can be used in gemstone design. Image height: approx. 16 mm, combination of transmitted light and incident side light (fiber-optics), crossed polarizers, first-order red compensator
- 19: Opal found in Ethiopia. Precious opal is a coveted gemstone due to its vivid play of spectral colors. This color play is formed by the submicroscopic structure of opal by SiO2-spheres the size of the wavelengths of visible light. If these spheres are uniform in size and evenly ordered, they produce a diffraction structure that splits white light into the spectral colors. Image height: approx. 12 mm, incident light (fiber-optics), HDRI tone mapping
- 20: Inclusion of a moth in Baltic amber, found on the East Baltic coast. See notes on image no 4. Image width: 12 mm, incident light (fiber-optics) in darkfield, HDRI tone mapping
- 21: Michael Hügi, M.Sc., Mineralogist, Gemmologist FGA, Bern, Switzerland uses stereomicroscopy to image inclusions in gemstones