GEOLOGY AND EXPLORATION OF GEM DEPOSITS AT MT. CARMEL, NORTHERN ISRAEL: NATURAL MOISSANITE, SAPPHIRE, RUBY & DIAMOND
On Mt Carmel, Late Cretaceous volcanic complexes intrude, and in places are interbedded with Cretaceous marine sediments. These intrusions, composed of volcaniclastic, extra-crater and basalt flow units, have alkali basalt to kimberlitic affinities.Sampling has recovered rare diamond , abundant moissanite and significant corundum, including sapphire and ruby, from these primary sources. Neogene uplift of the Mt Carmel block promoted the erosion of these primary sources, the products of which, inter alia the gem minerals of diamond, moissanite and corundum, were laid down in alluvial deposits along the Kishon Valley, mostly as low fluvial terraces, and in the Kishon graben as fluvial, marine and lagoonal sediments that were subjected to marine reworking during the Pliocene to Recent..
Some 30 moissanite crystals (<1 mm to 3.5 mm) were studied and confirmed to be natural moissanite (SiC 6H) by Raman spectroscopy. Morphology is hexagonal, bipyramidal to platy, with the pinacoid generally present, surfaces show etching (dissolution) and most are broken. The crystals are transparent with a color range from common deep blue to light green.
Corundum is present as two apparent populations, reflecting the two principal sources - Late Cretaceous volcanic bodies and Neogene basalts. The majority are sapphires of a dark blue mix often showing striations on the surface due to lamellar polysynthetic twinning. Others are usually smaller, with brighter colors of pink to red, or a violet-blue. Some are classified as ruby. Overall morphology shows bipyramidal to prism, with some pinacoid surfaces, often broken and etched.
Diamonds are white to grey, often included, and octahedral to THH in form. Most crystals show resorption, and most are fragments.
Highlights of the exploration include the recovery of 77 diamonds (to 0.88 carats, most <0.5 mm), approx. 2500 natural moissanite grains (to 4.1 mm) and more than 4000 sapphire and 400 ruby grains (to 5.72 carats for blue sapphire). Locally the gem mineral suite is sufficiently well concentrated in secondary deposits of the Kishon Valley to form placers.