Gemological and Mineralogical Studies of Greenish Blue Apatite in Madagascar

Abstract

Madagascar is known as the ‘Island of Gemstones’ because it is full of gemstone resources. Apatite from Madagascar is widely popular because of its greenish blue Paraiba-like color. This study analyzes apatite from Madagascar through standard gemological characteristic methods, spectroscopic tests and chemical analyses (i.e., electron probe and laser ablation inductively coupled plasma mass spectrometry). This work explores the gemological and the diagenesis information recorded on Madagascar apatite by comparing them with apatite from other sources and establishes the origin information of Madagascar apatite. The origin characteristics are as follows: Apatite from Madagascar is fluorapatite, with excellent diaphaneity, greenish–blue color caused by Ce and Nd and crystal structure distortion indicated by spectroscopic tests. The F/Cl ratio (16.47 to 21.89) suggests its magmatic origin Cl loss during the weathering processes forming the source rocks, and lg fO2 (−10.30 to −10.35) reflects the high oxidation degree of magma.

U–Pb Dating, Gemology, and Chemical Composition of Apatite from Dara-e-Pech, Afghanistan

“…The infrared absorption spectra of all the samples shared similarities at the main band peaks, suggesting consistencies in the molecular structures (see Figure 3a). The parameters of the doublet ~1060 and ~1109 cm −1 , corresponding to the ν 3 antisymmetric stretching vibration, significantly red-shifted and broadened compared with previous studies [34,35]. The ν 3 vibrations in the IR spectra of the fluorapatite appeared at 1029 and ~1095 cm −1 , which were significantly different from the samples in this study, as reported by Zolotarev et al (2018) [48] A study by Ulian [49] suggests that an increase in apatite structural defects and a decrease in the crystallinity broaden the ν 3 band and reduce its intensity.…”

“…In this research, the spectral characteristics of apatite produced in Afghanistan were compared with samples from various origins, including Durango from Mexico, blue apatite from Madagascar [35], and greenish-yellow apatite from Morocco [36]. The Afghanistan apatite was determined as fluorapatite according to the Raman spectra.…”

“…The Afghanistan apatite was determined as fluorapatite according to the Raman spectra. It is reported that the comparative apatite from Mexico, Madagascar, and Morocco are F-apatite as well [35,36,47]. The fluorapatite R050194 from the RRUFF database, produced in the Siglo XX deposit in the Larragua region of Bolivia, was selected in order to compare the differences in the IR spectra and Raman spectra.…”

“…In this section, apatite from various localities and generation environments are compared with the Afghanistan apatite, including AP (probably from Madagascar) [50], Otter Lake (Canada) from calcite [50], NW-1 (Ontario) from alkaline carbonatite [50], Slyudyanka (Lake Baikal) from metamorphic siliciclastic carbonate phosphogypsum [50], Durango (Mexico) from ion deposits [50], UWA-1 (Bancroft, Ontario) [50], Mud Tank (Austalia) from carbonatite [50], McClure Mountain (Colorado) from anorthite [50], SDG (Inner Mongolia, China) from alkaline ultramafic rocks [50], MADB (Madagascar) [35], and Moro (Anemzi, Morocco) [36]. Pegmatitic apatite from Madagascar (MAD) [38], the Central Iberian zone (CIZ) [51], and Xinjiang (Altay No.3 pegmatite) [52,53] are also used for origin identification.…”

Mineralogical Crystallography Volume II

“…Zhang et al [10] have studied apatite of Paraiba-like color from Madagascar. It was shown that studied samples belong to the fluorapatite mineral species.…”