Mineralogy, Petrography and Chemistry of Two Local Plasters, Iraq

The mineralogy, petrography and chemistry of two local plasters (Rasheed and Madae'n) and a dental stone were studied. Mineralogical study by x-ray diffraction spectrometer proved that the three gypsum products consist mainly of bassanite or hemihydrate (CaSO4. 0.5 H2O) with minor amounts of gypsum and anhydrite. The petrography of the studied thin sections, reveals that the two local plasters consist of dispersed prismatic, monoclinic crystals with ill-defined edges (bassanite of the β-hemihydrate). Dental stone consists of more packed, prismatic monoclinic crystals with well-defined and sharp edges (bassanite of the α–hemihydrate). Compressed powders of the two local plasters improved their crystal shapes and edges and made their outlines similar to dental stone or (α–hemihydrate). Chemical analyses of Rasheed and Madae'n plasters suggest that they consist of more than (96%) bassanite with small amounts of gypsum and anhydrite. Based on these compositions, the two local plasters are suitable for moulding, casting and constructional purposes. They are unsuitable for surgical plasters. ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ ــــــــــــــــــــــ ةيندعم يمحملا رتسلابلا نم نيعون ةيئايميكو ةيفا رغورتبو يروبجلا رابجلا دبع يكز ميها ربإ يدب ديشر ضرلأا مومع مسق ةيطفنلا تافاشكتسلاا ةكرش مومعلا ةيمك ا ةرا زو طفنل لصوملا ةعماج قا رعلا ،دادغب صخمملا مم ملا سبمجلاا رتمسلبلا نم نيعومن ةمينايميكو ةميفا رفورتبو ةميندعم ةمسا رد ممت ننادم لاو ديمشرلا رمج و ةدنا لا ةينيسلا ةعشلأا زايج ةطساوب ةيندعملا ةسا ردلا ت ضوأ .نانسلاا ا XRD ) نإ ةمثلثلا موسبجلا جتاون .تممميا رياينلااو مومممسبجلا نممم ةمممميمق تاممميمك رممم تيا ردمممياييميى وأ تيانمممساب ندمممعم نممم ةمممسينر ةرومممصب نومممكتت Zeki A. Aljubouri and Ibraheem R. Baddi 2 ةدمعابتم تا روممب نم نانوكتي م ملا رتسلبلا عون نأب جتاونلا هذى قي اسمل ةيفا رفورتبلا ةسا ردلا ت ضوأو تنم رمميف تاممفا تاذو لمميملا ةمميدا ا ةيروممشوم عوممن نمم تيانممسابا ةمم ظ β-hemihydrate ) . رممج نوممكتيو نمممم نانممممسلأا عوممممن نمممم تيانممممسابا ةمممم ظتنم تاممممفا تاذو اممممصا رت رممممثكا لمممميملا ةمممميدا ا ةيروممممشوم تا رومممممب α– hemihydrate لاكمشلأا نا نيمبت ، مم ملا رتمسلبلا نم نيعومنلا قو مسم سممع نيمعم طغمض طيمست دعبو . اممفا لاو امم اظتنا رممثكا ت بممصا ةمميرومبلا وبممشت تا رومممبلا هذممى نأو طاغممضنلاا ةمميممع لممبق امم م ا وممضو رممثكا ت نم ةبيرقو نانسلأا رج تا رومب ( α–hemihydrate .) ربكا ةبسنب تيانساب ندعم نم نانوكتي امينأب ننادملاو ديشرلا رتسلبل ةينايميكلا ليلا تلا ت ضوأو ( نم %96 ) مع ادامتعاو تيا ردياينلأاو موسبجلا نم ةميمق ةيمك رم نيعونلا نيذى نإف نايميكلا بيكرتلا س ةبلوقلا لامعلأ نا مصي رتسلبلا نم بصلاو ( moulding and casting كلذك ءانبلا لامعأو لاو ، ا ا رجلا رتسلبلا لامعتسلا نا مصي surgical plaster . ــــــــــــــــــــــــــــــــــــــــــــــــ ـــــــــــــــــــــــــــــــ ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــ ـــــــــ ـ INTRODUCTION A plaster is a calcined gypsum produced by heating the powdered raw material gypsum in rotary kilns at temperatures between (120) and (170° C) for a period of half to three hours. It is also called "Technical gyps". The use of the word "Technical" is to distinguish it from the local juss, which is also calcined gypsum but produced by rather primitive "Koor" method (Alrawas, 2002). Three bags of "Rasheed" plaster, each weighing about (30 Kg) were purchased from "Rasheed Gyps Factory", situated at about (20 Km) east of Tikrit city, on the Tikrit-Kirkuk main road. The gypsum raw material for the plaster is being brought from a nearby gypsum quarry belonging to Fat'ha Formation (Middle Miocene) (Baddi, 2009). Another three bags (30 Kg each) of Madae'n plaster were purchased from the local market in Mosul city. The plaster or gyps factory is in Falloja town (55 km west of Baghdad) and the raw material is being brought from "Mohammadi-Baghdadi" quarry (Fat'ha Formation, Middle Miocene) (Al-Qaraghooli, 1989). These two local plasters (Rasheed and Madae'n) were the only available types at the time of purchase. Three kilograms of German dental stone, type (Minridul) were purchased from local medical supply bureau and used as a standard reference. All materials were purchased during August (2007). The aim of this work is to study the mineralogy, petrography and chemistry of these two local plasters, and hence to know their proper industrial and medical applications. Mineralogy, Petrography and Chemistry of Two Local Plasters, Iraq 3