Gemstone Windows and Dark Patches: What to Look for in a Cut Gem

-
Image
AI-generated educational illustration. Conceptual only; not a photograph of an actual specimen or location. A coloured gem may have a pale, see-through centre or areas that look almost black. Both affect its appearance, but they do not have the same cause. What is a window? A window is an area where light passes through the gem instead of being returned towards the viewer. You may see the background through it, especially near the centre. Cutting angles and the material's refractive index—how it bends light—help determine whether this happens. There is no single ideal depth for every gemstone. Why dark patches need a closer look Darkness can have several causes. The material may absorb a lot of light. Some facets may reflect dark surroundings or the observer. Extinction is another cause, involving light that is not returned to the viewer after internal reflection. For that reason, calling every black patch “extinction” can be misleading. A simple viewing routine Look at the gem fac...
Post a Comment

Quartz with Anhydrite and clayey soil inclusions

-

 

Quartz with Anhydrite and clayey soil inclusions

A few days ago, a man brought a brownish-red crystal from Shakaradara, a village in the Kohat district of Khyber Pakhtunkhwa, Pakistan, for testing purposes.

Quartz with Anhydrite
from Shakaradara, a village in the Kohat district of Khyber Pakhtunkhwa, Pakistan


Upon examination, it was observed that the crystal had a pyramid formation and a short hexagonal prism. Additionally, the refractive index of the naturally polished surface was measured to be between 1.542 and 1.550. These characteristics confirmed that the crystal in question was indeed quartz.

Quartz with anhydrite and clayey inclusions
from Shakaradara, a village in the Kohat district of Khyber Pakhtunkhwa, Pakistan


To further confirmation, the crystal was subjected to analysis using the Private Raman Spectroscopy facility. The results revealed the presence of Anhydrite mineral inclusions within the quartz crystal. Moreover, the obtained Raman spectra perfectly matched those found in the RRUFF Raman spectra library.




The question regarding the reddish color of this quartz arises from the fact that it is found in an area with clayey soil that has a reddish hue, possibly due to a higher concentration of iron oxide. As the quartz forms, it becomes trapped within this soil, resulting in its distinctive coloration.

Quartz specimen with anhydrite and clayey inclusions
from Shakaradara, a village in the Kohat district of Khyber Pakhtunkhwa, Pakistan


Below, you will find the combined (Quartz + anhydrite) and individual anhydrite Raman spectra.
Combined Raman spectra of quartz and anhydrite
Quartz and Anhydrite combine Raman spectra

Raman spectrum of anhydrite
Anhydrite Raman Spectra 


Hamid Usman

Gemologist

CIGTL-Gemological Laboratory of Pakistan at Peshawar. 

“Correct me if I’ve misunderstood“

"Similar Topics"☝☝

petroleum quartz☝☝

Why Quartz is some common?☝☝




Comments

Post a Comment

Post a Comment Please. we love hearing from you.

Popular posts from this blog

Introduction quiz

-
💎 Gemology Quiz 1. What does gemology study? The study of rocks only The study of gemstones and their properties The study of fossils 2. Who is a gemologist? A person who mines gemstones A person who designs jewelry A person who identifies gemstones using instruments 3. Which of the following is NOT a characteristic of a mineral? Naturally occurring Organic in nature Has a defined chemical composition 4. What makes a gemstone valuable? Only its size Beauty, rarity, and durability Color only 5. Which of the following is an organic gem? Sapphire Pearl Emerald 6. The Mohs scale measures what property? Toughness Hardness Transparency Submit Quiz Further reading introduction to gemology Gemology MCQs Part-1
Read the full guide

Gemology MCQs Part-3

-
Image
Gemology MCQs Gemology Multiple-Choice Questions 21. Separating natural pink sapphire from synthetic pink sapphire commonly relies upon a microscopic study. True False 22. In a round brilliant cut, the total number of facets is: 57 59 60 None of the above 23. A spectroscope is used to detect the spectrum. True False 24. Refraction is the bending of light. True False ...
Read the full guide

Gemology MCQ Quiz Part 6: Test Your Gemstone Knowledge

-
Image
Gemstone MCQs Quiz Test Your Knowledge in Gemology Part 6 1. A 2-carat fine-quality ruby is worth more than 10 rubies of the same color and quality, which have a total weight of 4 carats . a) True b) False Correct Answer: a) True 2. One carat equals: a) 1 gram b) 1/10 of a gram c) 1/5 of a gram d) 1/2 of a gram Correct Answer: c) 1/5 of a gram 3. A ten-pointer is a stone that weighs: a) 10 carats b) 1/10 of a carat c) 10 facet junctions d) 10 grams Correct Answer: b) 1/10 of a carat 4. When comparing gem prices, you should compare their: a) Per-carat cost b) Overall size c) Density d) Facet count ...
Read the full guide