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Ferric iron (Fe 3+) gives a pale yellow color in plagioclase feldspar from Lake County, Oregon. [18] The specific gravity increases smoothly with calcium content, from 2.62 for pure albite to 2.76 for pure anorthite, and this can provide a useful estimate of composition if measured accurately. [8]
The ratio of alkali feldspar to plagioclase feldspar, ... The specific gravity in the plagioclase series increases from albite (2.62) to anorthite (2.72–2.75).
Albite is a plagioclase feldspar mineral. ... pinacoidal forms. Its specific gravity is about 2.62 and it has a Mohs hardness of 6 to 6.5.
Specific gravity: 2.72–2.75: Optical properties: ... Anorthite (an = not, ortho = straight) is the calcium endmember of the plagioclase feldspar mineral series.
The specific gravity of bytownite varies between 2.74 and 2.75. The refractive indices ranges are nα=1.563 – 1.572, nβ=1.568 – 1.578, and nγ=1.573 – 1.583. Precise determination of these two properties with chemical, X-ray diffraction , or petrographic analysis are required for identification.
Labradorite ((Ca, Na)(Al, Si) 4 O 8) is a calcium-enriched feldspar mineral first identified in Labrador, Canada, which can display an iridescent effect . Labradorite is an intermediate to calcic member of the plagioclase series. It has an anorthite percentage (%An) of between 50 and 70. The specific gravity ranges from 2.68
The plagioclase feldspars are a continuous solid solution series and as such the accurate identification of individual members requires detailed optical study, chemical analysis or density measurements. Refractive indices and specific gravity increase directly with calcium content. [5] It is sometimes used as a gemstone. [6]
Specific gravity: 2.55–2.63: Optical properties: ... It is a type of potassium feldspar, ... (NaAlSi 3 O 8), of plagioclase.