Tolkien's art - Lake Mithrim

Question

Scratching my head here trying to work out what object or event is represented by the bright golden triangle in the background.

Any ideas? Please don't tell me it is Thangorodrim! Perhaps it is the sun breaking through, but it looks too solid for that.

Answer 1

According to Wayne Hammond and Christina Scull this is indeed Thangorodrim

In J.R.R.Tolkien: Artist and Illustrator, Tolkien scholars Wayne Hammond and Christina Scull discuss this image and they conclude that the peak left of center is probably Thangorodrim, mainly on the basis of a passage Tolkien wrote around the same time which said that the peak of Thangorodrim was visible from Lake Mithrim.

It also may be that his artistic talents responded to a sense of security he now felt in his family and profession, and by now he had explored the world of 'The Silmarillion' for more than a decade, and felt more confident in rendering his invented landscapes.
Among these was the land of Hisilómë, also called Hithlum or Dorlómin, the land of shadows. In this region was the lake, Mithrim, on the opposite shores of which the divided hosts of the Gnomes (Noldorin Elves) camped on their return to Middle-earth, until their feud was ended and they united in opposing Morgoth. The lake is mentioned in The Book of Lost Tales but not described until later: it had 'wide pale waters', it was a 'great lake', its 'mighty waters reflect a pale image of the encircling hills'. Both lake and hills can be seen in the painting Tolkien made in Lyme Regis in 1927. The peak in the distance, left of centre, is probably Thangorodrim: the contemporary Sketch of the Mythology implies that the hosts of Gnomes on either side of Mithrim could see the 'vast smokes and vapours . . . made and sent forth from Angband, and the smoking top of Thangorodrim (the highest of the Iron Mountains around Morgoth's fortress)'. Except for a few lines to represent trees, Tolkien made no attempt to depict the shoreland woods noted in some of his texts; but the mists that lay around the lake obscured many things.
_{J.R.R.Tolkien: Artist and Illustrator, page 50}

This passage of Tolkien's being referenced reads in full:

The Sun rises as they march, their blue and silver banners are unfurled, flowers spring beneath the feet of their armies. The Orcs dismayed at the light retreat to Angband. But there is little love between the two hosts of Gnomes encamped now on opposite shores of Mithrim. Vast smokes and vapours are made and sent forth from Angband, and the smoking top of Thangorodrim (the highest of the Iron Mountains around Morgoth's fortress) can be seen from far away. The North shakes with the thunder under the earth. Morgoth is forging armouries. Finweg resolves to heal the feud. Alone he goes in search of Maidros. Aided by the vapours, which are now floating down and filling Hithlum, and by the withdrawal of Orcs and Balrogs to Angband, he finds him, but cannot release him.
_{The Shaping of Middle-earth, "Sketch of the Mythology" §8}

Also, here is a somewhat clearer picture of the object in question. (Note that in the original painting, this mountain is under half a centimeter across.)

_{Mithrim (detail)}