By: Abdulkader M. Abed
[Many Muslim scholars dealt with minerals and gems and wrote monographs on the subject. The golden age of their writings was the 4th-5th century after Hijra (AH) (10th-11th century CE). They used almost all the physical properties now known to us to identify and differentiate minerals. Experimentation was a widespread habit in the study of minerals. Al-Biruni, in the author’s view, was the leading scientist in this subject.]
Introduction
Mineralogy is the science studying “minerals”. A mineral is a naturally occurring substance that has a definite chemical composition and crystal structure. In other words, a mineral is a crystalline, chemically pure, natural material. Accordingly, gold, diamond, quartz, calcite, sapphire and pearl are examples of minerals. The importance of minerals and mineral resources are well known and do not need to be mentioned here.
Gems and precious stones are special types of minerals. They are rare, beautiful (in colour, transparency, and lustre), and hard enough to resist physical and chemical changes for some time. Diamond, ruby, sapphire, and emerald have these properties; they are gems and, of course, minerals. The importance of gems to emperors, kings and wealthy women was possibly the driving force behind their recognition since the dawn of human civilisation.
Certain varieties of mineral, precious stones, and gems were known to the Ancient Egyptian, Mesopotamian, Ancient Indian, Greek, and Roman people. Most of the lands of these people became part of the Islamic State or “Caliphate”. Consequently, their writings on gems and minerals, as was the case with other subjects, were translated into Arabic in the first three centuries AH (6th to 8th CE). Therefore it is not surprising to find the best contributions by Muslim scientists to mineralogy and gemology was in the 10th and 11th centuries CE.
- Scientists of the Subject
Most of what was written on the subject of minerals, stones, and gems was lost. However, a few monographs survived, and these are now in print. Additionally, information on the subject can be found in some encyclopedic works. These are some examples:
* Yahya Bin Masawaih (died 242 AH/857 CE), Gems and their properties.
* Al-Kindi, Ya’koub Bin Ishaaq (260AH/873CE) wrote three monographs, the best of which is “Gems and the Likes”. It was cited by other writers in the subject. However, has seen been lost.
* Al-Hamdani, Al-Hasan Bin Ahmad (334AH/947CE) wrote three books on Arabia in parts of which he described methods of exploration for gold, silver, and other minerals and gems, their properties and locations.
* bIkhwaan As-Safa (2nd half of the 4th century AH) wrote an encyclopaedic work, which included a part on minerals, particularly their classification.
* Al-Biruni, Abu Ar-Rayhan Mohammad Bin Ahmad (440AH/1048CE) is in the authors view the leading mineralogist throughout Islamic history. His monograph “Treatises on how to recognise gems”(Al-Jamhir fi Ma’rifatil Al-Jawahir) is most probably the best contribution on mineralogy in the Muslim civilisation. Throughout this manuscript, Al-Biruni did not translate or copy the science of other civilisations but Instead, he recorded his own experience.
* AI-Tifashi, Ahmad Bin Yousef’s (683AH), “Flowering Ideas on Gemstones”(Azhar Al-Afkar fi Jawahir Al-Ahjar), although more than 200 years after the work of Al-Biruni, is of lower scientific value. However, it is much superior both in classifying minerals and in the method of studying them, which is very close to what we now observe in contemporary books on mineralogy.
* Ibn Al-Akfani, Mohammad Bin Ibrahim (749AH/1348AD), “Special Treasures on Characteristics of Gemstones” (Nukhab Al-Thakhair fi Ahwaal Al-Jawahir). This monograph is scientifically of lesser quality than that of Al-Tifashi.
3- Methods of Study
From the dawn of human civilisation up until the 18th century CE, minerals were studied by the use of their physical properties; e.g. colour, lustre, hardness and crystal habit. Whilst Muslim scientists used the same set of physical properties as scholars preceding and succeeding them, they also made original contributions to the subject. The following are some examples of these properties and how they were used by Muslim scientists to identify certain minerals.
3.1- Colour
Colour is what you see with the naked eye in the specimens. It was used extensively to subdivide a gem into several varieties. Yaghout (-),y9li), now known as corundum, was divided into four types; each was subdivided into several varieties.
* Red = present day ruby. Seven varieties were identified.
* Yellow = Yellow sapphire. Five varieties were identified.
* Blue = sapphire. Five varieties were identified.
* White = white sapphire
Since colour is misleading in the identification of minerals, it is important to emphasise their ability to place all these coloured varieties in one gem category: Yaghout or corundum. To do this, they depended on other properties beside colour.
3.2- Streak
Streak is the colour of the mineral powder when scratched. It is still used now to differentiate, for example, between minerals which have the same colour but vary in their streak colour. This property was used by AlBiruni to group several varieties of hematite Fe203 (Shathenj ia) under one mineral.
3.3- Dispersion
This is the ability of a mineral to analyse the white light into its seven components, violet – red. Diamond is one of the minerals which have this property. To Muslim scholars, the higher the quality of diamond, the better it disperses light.
3.4- Hardness
Hardness is the ability of a mineral to scratch other minerals. The scratched mineral is the softer of the two. This property was well known to Muslim scholars, to the degree that they arranged the known minerals according to their hardness. Al-Biruni wrote in his monograph “Al-Jamaher …” p. 66″: “I have started my book describing diamond before all other gems because it is the leader or master. It scratches Yaghout (corundum) and Yaghout scratches what comes below it. However, Yaghout cannot scratch diamond. … etc” (Author’s translation). This is exactly our present knowledge of both minerals. Al-Biruni also differentiated between diamond and a variety of quartz by hardness. A lot has been written on this property; these few lines are sufficient to explain the idea.
3.5- Habit
Habit is the most common natural form or shape of the mineral. It is a reflection of its crystal form. This important property was also frequently used by Muslim scholars to differentiate between minerals. Let us translate the habit of diamond from Al-Tiefashi (author’s translation): “… and of the properties of diamond, all types have right angles, six or eight or more, the faces are triangles. If it is broken, faces will be triangular even at the smallest parts …” This is true because we now know that diamond is of the cubic crystal system, and its more important habit is the octahedron.
Al-Biruni, p. 94-95 differentiated between diamond and Yaghout, and diamond and quartz using the crystal habit. Figures 1 and 2 are drawn by the author according to the descriptions of AI-Biruni.