Korundum

Korundum
Umum
KategoriMineral
Rumus
(unit berulang)		aluminium oksida, Al2O3
Sistem kristalTrigonal (Heksagonal Scalenohedral)
Identifikasi
WarnaCoklat hingga abu-abu, lebih jarang merah, biru, putih, kuning.
PerawakanBipiramida, memapan (tabular), prismatik, kristal rombohedral, butiran, atau tak beraturan (massive)
Bentuk kembaranPolisintetik umum ditemukan
FrakturMembulat (conchoidal) hingga kasar tak teratur (uneven)
Kekerasan dalam skala Mohs9
KilauKilap kaca hingga permata
GoresPutih
Berat jenis3.95-4.1
Indeks biasnω=1.768 - 1.772 nε=1.760 - 1.763, Biref 0.009
PleokroismeTidak ada
FusibilitasInfusible
Kelarutantidak larut
Variasi utama
SafirSemua warna kecuali merah
RubiMerah
EmeriButiran

Korundum (dari Bahasa Tamil: kurundam) adalah kristal aluminium oksida dan merupakan salah satu mineral pembentuk batuan. Secara alami mineral ini jernih, tetapi dapat memiliki warna yang berbeda dengan adanya zat pengotor. Spesimen yang transparan digunakan sebagai batu permata, yang disebut rubi jika berwarna merah dan safir jika berwarna selain merah. Selain kekerasannya, korundum dikenal karena densitasnya yang tinggi (4,02 g/cm³), yang sangat tinggi untuk suatu mineral transparan yang tersusun dari unsur ber-massa atom rendah aluminium dan oksigen.

Sifat

Dalam skala Mohs, korundum merupakan mineral dengan tingkat kekerasan yang tinggi. Nilainya berada pada tingkat 9. Jenis mineral pada tingkat 9 memiliki sifat permukaan yang dapat menggores kaca.[1]

Referensi

  1. ^ Fitri, Yuni Rahma (2015). 1001 Aksesori dari Batu Mulia: Ensiklopedi dan Tutorial Craft. Jakarta: Penerbit PT Gramedia Pustaka Utama. hlm. 6. ISBN 978-602-03-2646-7. 

Bacaan lanjutan

  • Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., Wiley, pp. 300-302 ISBN 0-471-80580-7
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